CN1882599A - Process for recovering a crystalline product from solution - Google Patents

Abstract

An improved process for recovering a crystalline product (particularly an N-(phosphonomethyl)glycine product) from a solution comprising both a product subject to crystallization and undesired impurities is provided.

Description

Method for recovering crystalline product from solution

Field of the invention

The present invention relates generally to methods for the production and recovery of crystalline products from solutions containing readily crystallizable products and undesired impurities. More specifically, the present invention relates to a process for the production and recovery of N-(phosphonomethyl)glycine product from aqueous reaction solutions prepared by liquid phase oxidation of N-(phosphonomethyl)iminodiacetic acid substrates.

Background of the invention

N-(phosphonomethyl)glycine is described by Franz in US Patent No. 3,799,758. N-(phosphonomethyl)glycine and its salts are conveniently included as an ingredient in aqueous, post-emergence herbicide formulations. As such, they are especially useful as highly effective and commercially important broad-spectrum herbicides for killing or controlling the growth of a wide variety of plants, including germinating seeds, seedlings, mature and established woody , and herbaceous and aquatic plants.

One of the very widely accepted methods for making N-(phosphonomethyl)glycine products involves the liquid-phase oxidative cleavage of carboxymethyl substituents from N-(phosphonomethyl)iminodiacetic acid substrates . "N-(phosphonomethyl)iminodiacetic acid substrate" as used herein includes N-(phosphonomethyl)iminodiacetic acid and its salts, wherein the salt-forming cation is, for example, ammonium, alkylammonium, Alkali or alkaline earth metals. Over the years, various methods and reactor systems have been disclosed for carrying out this oxidation reaction. See generally Franz et al., Glyphosate: A Unique Global Herbicide (ACS Monograph 189, 1997), pp. 233-62 (and references cited therein); Franz, US Patent No. 3,950,402; Hershman, US Patent No. 3,969,398 ; Felthouse, US Patent No. 4,582,650; Chou, US Patent No. 4,624,937; Chou, US Patent No. 4,696,772; Ramon et al., US Patent No. 5,179,228; Siebenhaar et al., International Publication No. WO 00/01707; et al., US Patent No. 6,417,133; Leiber et al., US Patent No. 6,586,621; and Haupfear et al., International Publication No. WO01/92272.

Liquid-phase oxidation of the N-(phosphonomethyl)iminodiacetic acid substrate typically produces a reaction mixture containing water and various impurities in addition to the desired N-(phosphonomethyl)glycine product . These impurities may include, for example, various by-products, unreacted starting materials, and impurities present in the starting materials. Representative examples of impurities present in the N-(phosphonomethyl)glycine product reaction mixture include unreacted N-(phosphonomethyl)iminodiacetic acid substrate, N-formyl-N-(phosphono Methyl)glycine, phosphoric acid, phosphorous acid, hexamethylenetetramine, aminomethylphosphonic acid (AMPA), methylaminomethylphosphonic acid (MAMPA), iminodiacetic acid (IDA), formaldehyde, formic acid, chlorine compounds and so on. The value of the N-(phosphonomethyl)glycine product generally determines the maximum recovery of the product from the reaction mixture and often also provides for recycling (e.g., to the oxidation reactor system) of at least a portion of the depleted reaction mixture. ) in order to achieve further conversion of unreacted substrate and recovery of product as a driving factor.

Commercial considerations also sometimes dictate that the concentration of the N-(phosphonomethyl)glycine product in the commercially available mixture is significantly greater than in the reaction mixture typically formed in an oxidation reactor system, especially when the N-(phosphonomethyl)glycine product When the methyl)glycine product is stored or transported for agricultural use. For example, when a heterogeneous catalyst is used for the liquid phase oxidation of N-(phosphonomethyl)iminodiacetic acid to produce N-(phosphine In the case of acyl)glycine, in general, it is preferred to keep the maximum concentration of the N-(phosphonomethyl)glycine product in the reaction mixture no greater than about 9% by weight in order to keep the product in solution, although more than 9% and even Higher concentrations up to about 12% by weight may suitably be used at higher reaction mixture temperatures. Sometimes, however, it is desirable to have a commercially available mixture with a much higher concentration of N-(phosphonomethyl)glycine. Thus, after the N-(phosphonomethyl)glycine product has been formed and, if desired, separated from the catalyst, it is generally preferred to concentrate the product and separate it from various impurities in the oxidation reaction mixture.

Smith, in US Patent No. 5,087,740, describes a method of purifying and concentrating the N-(phosphonomethyl)glycine product. Smith discloses passing the reaction mixture containing N-(phosphonomethyl)glycine through a first ion exchange resin column to remove impurities more acidic than N-(phosphonomethyl)glycine, allowing the The effluent from the resin column is passed through a second ion exchange resin column capable of adsorbing N-(phosphonomethyl)glycine, and N-(phosphonomethyl)glycine is recovered by passing a base or a strong mineral acid through the second ion exchange resin column. ) Glycine.

Haupfear et al. in International Publication No. WO01/92272 describe a method for the purification and concentration of the N-(phosphonomethyl)glycine product prepared by oxidation of the N-(phosphonomethyl)iminodiacetic acid substrate . Haupfear et al. describe the production of two crystalline N-(phosphonomethyl)glycine products in two separate crystallizers, where the crystals are of two different purities. The lower purity material can then be blended with the higher purity material to produce a single product of acceptable purity.

There remains a need for methods of producing and recovering crystalline products from solutions containing readily crystallizable products and undesired impurities that are capable of producing multiple product mixtures containing crystalline products, each exhibiting a suitable impurity profile for the intended use . There is a particular need for methods for the production and recovery of crystalline N-(phosphonomethyl)glycine products from reaction solutions prepared by oxidation of N-(phosphonomethyl)iminodiacetic acid substrates which are capable of producing marketable Both the N-(phosphonomethyl)glycine wet cake product and the concentrated liquid or solid salts of N-(phosphonomethyl)glycine of acceptable purity for formulation of herbicidal compositions. Such an approach would improve the overall flexibility to adequately support the market demand for various N-(phosphonomethyl)glycine products.

Summary of the invention

It is therefore certain objects of the present invention to: provide an improved process for recovering one or more crystalline products from a solution containing both a product that readily crystallizes from solution and an undesired impurity; provide that the crystalline product can be produced without washing A method of producing one or more crystalline products of acceptable purity; providing the ability to recover one or more crystalline products of acceptable purity when filter cake washing is insufficient to remove entrapped impurities from the crystalline product A method; providing a method for recovering one or more N-(phosphonomethyl)glycine products from a slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and mother liquor; providing the ability to produce A variety of suitable crystalline products, such as wet cake products, thereby providing a method for greater process flexibility; and a method for recovering crystalline products of acceptable purity with better handling and packaging characteristics method.

Thus, briefly, one aspect of the present invention relates to a method of preparing crystalline products (eg, wet cake products) from a solution containing both a product that readily crystallizes from solution and an undesired impurity. In one embodiment, the method comprises: dividing the solution into a plurality of fractions comprising a primary fraction and a secondary fraction, and precipitating product crystals from the primary fraction in a first crystallization operation to produce precipitated product comprising Primary product slurry of crystals and primary mother liquor. Product crystals are likewise precipitated from the secondary fraction in a second crystallization operation to produce a secondary product slurry comprising precipitated product crystals and secondary mother liquor. Precipitated product crystals are separated from the primary product slurry in a first liquid/solid separation step to produce a first wet cake product and a primary mother liquor fraction. The precipitated product crystals are likewise separated from the secondary product slurry in a second liquid/solid separation step to produce a second wet cake product and a secondary mother liquor fraction. At least a portion of each mother liquor fraction is recycled such that unrecovered products and impurities contained therein are reintroduced into one or both of the crystallization operations. In addition, the impurity content of each wet cake product is controlled or maintained below a defined value by (i) netting the impurities contained in one of the first and second mother liquor fractions transferred to another of the first and second crystallization operations; (ii) net transfer of impurities contained in one of the first and second mother liquor fractions to the first and second liquid/ In another step among the solids separation steps; (iii) net transfer of the lower impurity content wet cake product obtained from one of the first and second liquid/solids separation steps to the first and second crystallization operations In another operation in; (iv) net transfer the wet cake product with lower impurity content obtained from one of the first and second liquid/solid separation steps to the first and second liquid/solid separation steps (v) net transferring the slurry with lower impurity content obtained from one of the first and second crystallization operations to the other of the first and second crystallization operations; (vi) net transfer of the lower impurity content slurry obtained from one of the first and second crystallization operations to the other of the first and second liquid/solid separation steps; or (i) , (ii), (iii), (iv), (v) and/or (vi) in combination.

In particular, the present invention relates to a process for recovering one or more crystalline N-(phosphonomethyl)glycine products, such as various wet cake products, from an aqueous oxidation reaction solution comprising N-(phosphonomethyl)glycine products, wherein in The impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is controlled.

In one such embodiment, the aqueous reaction solution comprising the N-(phosphonomethyl)glycine product is first divided into fractions comprising a primary fraction and a secondary fraction. N-(phosphonomethyl)glycine product crystals are precipitated from the primary fraction to produce a primary product slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and primary mother liquor. The primary product slurry is divided into a first portion and a second portion, and precipitated N-(phosphonomethyl)glycine product crystals are separated from the first portion of the primary product slurry, thus producing a first N-(phosphonomethyl)glycine product crystal Methyl)glycine wet cake product. The second portion of the primary product slurry is combined with the N-(phosphonomethyl)glycine product contained in or obtained from the secondary fraction of the aqueous reaction solution. A secondary fraction of the aqueous reaction solution is subjected to an evaporative crystallization operation to precipitate N-(phosphonomethyl)glycine product crystals from the secondary fraction, thereby producing crystals comprising precipitated N-(phosphonomethyl)glycine product and Secondary evaporation product slurry of secondary mother liquor. Precipitated N-(phosphonomethyl)glycine product crystals are separated from the secondary evaporation product slurry to produce a second N-(phosphonomethyl)glycine wet cake product.

In another embodiment of the present invention, a method for recovering N-(phosphonomethyl)glycine product from an aqueous oxidation reaction comprising N-(phosphonomethyl)glycine product comprises dividing the aqueous reaction solution into a fraction comprising a primary fraction and Multiple fractions of secondary fractions. N-(phosphonomethyl)glycine product crystals are precipitated from the primary fraction to produce a primary product slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and primary mother liquor. The precipitated N-(phosphonomethyl)glycine product crystals are separated from the primary product slurry to produce a first N-(phosphonomethyl)glycine wet cake product. At least a portion of the first N-(phosphonomethyl)glycine wet cake product is mixed with N-(phosphonomethyl) contained in or obtained from the second fraction of the aqueous reaction solution. ) combined with glycine products. N-(phosphonomethyl)glycine product crystals are precipitated from the secondary fraction of the aqueous reaction solution in an evaporative crystallization operation to produce a distillate comprising precipitated N-(phosphonomethyl)glycine product crystals and a secondary mother liquor. Grade evaporation product slurry. Precipitated N-(phosphonomethyl)glycine product crystals are separated from the secondary evaporation product slurry to obtain a second N-(phosphonomethyl)glycine wet cake product.

In yet another embodiment of the present invention, a method for recovering N-(phosphonomethyl)glycine product from an aqueous oxidation reaction comprising N-(phosphonomethyl)glycine product comprises dividing the aqueous reaction solution into a primary fraction and Multiple fractions of secondary fractions. N-(phosphonomethyl)glycine product crystals are precipitated from the primary fraction to produce a primary product slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and primary mother liquor. N-(phosphonomethyl)glycine product crystals are also separated from the secondary crystallization feedstock mixture comprising a secondary fraction of the aqueous reaction solution and at least a portion of the primary product slurry to produce N-(phosphonomethyl)glycine comprising precipitate base) secondary product slurry of glycine product crystals and secondary mother liquor. The precipitated N-(phosphonomethyl)glycine product crystals are separated from the secondary product slurry to produce a wet cake of N-(phosphonomethyl)glycine product.

In other embodiments, the method for recovering N-(phosphonomethyl)glycine product from an aqueous oxidation reaction comprising N-(phosphonomethyl)glycine product comprises dividing the aqueous reaction solution into a primary fraction and a secondary fraction and precipitating N-(phosphonomethyl)glycine product crystals from the primary fractions to produce a primary product slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and primary mother liquor. N-(phosphonomethyl)glycine product crystals are also precipitated from an aqueous secondary crystallization feed mixture comprising a secondary fraction of the aqueous reaction solution to produce precipitated N-(phosphonomethyl)glycine product crystals and di The secondary product slurry of the primary mother liquor. At least a portion of the primary product slurry is combined with at least a portion of the secondary product slurry to produce a secondary fraction product mixture from which precipitated N-(phosphonomethyl)glycine product crystals are separated to produce N -(phosphonomethyl)glycine wet cake product.

In still other embodiments of the present invention, a method for recovering N-(phosphonomethyl)glycine product from an aqueous oxidation reaction comprising N-(phosphonomethyl)glycine product comprises separating the aqueous reaction solution into and secondary fractions, and precipitate N-(phosphonomethyl)glycine product crystals from the primary fraction in a first crystallization operation to produce precipitated N-(phosphonomethyl)glycine containing Primary product slurry of product crystals and primary mother liquor. N-(phosphonomethyl)glycine product crystals are also precipitated from the secondary fraction comprising the aqueous reaction solution in a second crystallization operation to produce precipitated N-(phosphonomethyl)glycine product crystals and secondary Secondary product slurry of mother liquor. The precipitated N-(phosphonomethyl)glycine product crystals are separated from the primary product slurry in a first liquid/solid separation step to obtain a first wet cake product and a primary mother liquor fraction, as well as precipitated N-(phosphonomethyl)glycine product crystals. The methyl)glycine product crystals are separated from the secondary product slurry in a second liquid/solid separation step to yield a second wet cake product and a secondary mother liquor fraction. At least a portion of each mother liquor fraction is recycled such that unrecovered N-(phosphonomethyl)glycine product and impurities contained therein are reintroduced into one or both of the crystallization operations. In addition, the impurity content of each wet cake product may be kept below a defined value by net transfer of impurities contained in one of the first and second mother liquor fractions to: (i) the other of the first and second crystallization operations; (ii) the other of the first and second liquid/solid separation steps; (iii) the other of the first and second wet cake products or any combination of (i), (ii) and/or (iii).

The present invention also relates to a process for recovering N-(phosphonomethyl)glycine product from a slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and a mother liquor. In a first embodiment, the method includes dividing the slurry into multiple fractions including a first slurry fraction and a second slurry fraction. Precipitated N-(phosphonomethyl)glycine product crystals are separated from the first and second slurry fractions to produce a first wet cake product and a second wet cake product, respectively. The ratio of the solids content of the second wet cake product to the solids content of the first wet cake product is at least about 1.1 as measured by weight percent solids in the first and second wet cake products.

In another embodiment, the method for recovering N-(phosphonomethyl)glycine product from a slurry comprising precipitated N-(phosphonomethyl)glycine product crystals and mother liquor comprises separating the slurry into a slurry comprising first and Various fractions of the second slurry fraction. The first slurry fraction is introduced into a first liquid/solid separation device, wherein precipitated N-(phosphonomethyl)glycine product crystals are separated from the first slurry fraction to produce a first wet cake product. The second slurry fraction is introduced into a second liquid/solid separation device parallel to the first liquid/solid separation device, and wherein the precipitated N-(phosphonomethyl)glycine product crystals are extracted from the second slurry fraction separated to produce a second wet cake product. The second wet cake product has a higher solids content, as measured by weight percent solids in the wet cake product, than the first wet cake product.

Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.

Brief description of the drawings

Figure 1 is a schematic flow diagram of an embodiment of the invention for recovering wet cake products having different solids contents from product slurries using two separate liquid/solid separation systems or devices in parallel, the product slurries being obtained by crystallization It is produced by concentrating a solution containing a product that readily crystallizes from solution in this stage.

Fig. 2 is the oxidation of N-(phosphonomethyl)hydrogenediacetic acid substrate in the reactor system to form the oxidation reaction solution containing N-(phosphonomethyl)glycine product and the parallel use of first adiabatic and second Schematic flow diagram of the overall process for recovering two crystalline N-(phosphonomethyl)glycine wet cake products from the oxidation reaction solution with a non-adiabatic evaporative crystallization stage and a separate liquid/solid separation system or device.

Figure 3 is a schematic flow diagram of the process depicted in Figure 2, wherein the impurity distribution among the crystalline N-(phosphonomethyl)glycine wet cake product is obtained by separating the product slurry or paste from a first adiabatic crystallization The net transfer of the system to the product slurry of the second non-adiabatic evaporative crystallization system is controlled.

Figure 4 is a schematic flow diagram of the process depicted in Figure 2, wherein the impurity distribution among the crystalline N-(phosphonomethyl)glycine wet cake product is obtained by separating the product slurry from the first adiabatic crystallization system The net transfer to the second non-adiabatic evaporative crystallization stage is controlled.

Figure 5 is a schematic flow diagram of the process described in Figure 2, wherein the impurity distribution among the crystalline N-(phosphonomethyl)glycine wet cake product is determined by adding the N-(phosphonomethyl)glycine product crystals Net transfer from the first adiabatic crystallization system to the product slurry in the second non-adiabatic evaporative crystallization system is controlled.

Figure 6 is a schematic flow diagram of the process described in Figure 2, wherein the impurity profile among the crystalline N-(phosphonomethyl)glycine wet cake product is obtained by separating the impurities contained in the mother liquor from a first adiabatic A crystallization operation and/or a second non-adiabatic evaporative crystallization operation controlled by a net transfer to: (i) another of the adiabatic and/or evaporative crystallization operations; (ii) adiabatic and/or evaporative liquid / another of the solids separation steps; (iii) another of the adiabatic or evaporating wet cake product; or any combination of (i), (ii) and/or (iii).

Detailed Description of the Preferred Embodiment

In accordance with the present invention, it has been found that the production and recovery of various crystalline wet cake products (particularly N-(phosphonomethyl)glycine wet) from one or more solutions containing easily crystallized products and undesired impurities cake product) methodological improvements. Typically, at least one of the recovered crystalline products is of acceptable purity, and any other recovered crystalline product is of acceptable purity capable of being blended with one or more other crystalline products to form pure product, and/or can be further processed or blended to form a wet cake or concentrated liquid or solid salt of N-(phosphonomethyl)glycine with acceptable purity for use in the formulation of herbicidal compositions . Typically, an N-(phosphonomethyl)glycine wet cake of acceptable purity contains at least about 95% by weight N-(phosphonomethyl)glycine product (on a dry basis) and the remainder is impurities such as reaction by-products , unreacted starting material and impurities present in the starting material. Each impurity may have its own concentration specification.

Without wishing to be bound by a particular theory, it has been found that by separating various wet cakes having different solids contents, different impurity concentrations and/or different crystal size distributions from one or more product slurries containing precipitated products and impurities The impurity content of the product, the wet cake product, is more effectively controlled, thus providing greater process flexibility. The method of the present invention is particularly desirable for use in the concentration and recovery of crystalline products in those processes where conventional filter cake washing steps are undesirable or insufficient to produce a product of acceptable purity. For example, it has been found that the process of the present invention is effective in producing a wet cake product of acceptable purity even when the product crystals precipitated from solution contain impurities that are entrapped or otherwise introduced into the solid, these Impurities cannot be efficiently or practicably removed by ordinary filter cake washing methods or by other measures such as reslurrying with water or recrystallization. Additionally, the improved method of the present invention may also allow for the production of wet cake products with improved packaging and handling characteristics.

It is important to point out that the strategy elucidated here has broad application prospects in the preparation of reaction solutions containing readily crystallizable products and in methods for concentrating and recovering wet cakes of crystallized products from reaction solutions. The present invention is particularly useful for concentrating and recovering wet cake products from oxidation reaction solutions containing readily crystalline N-(phosphonomethyl)glycine products and especially those containing N-(phosphonomethyl)glycine, wherein The oxidation reaction solution is produced by the catalytic liquid phase oxidation of the N-(phosphonomethyl)iminodiacetic acid substrate. It should be understood, however, that the present invention is equally applicable to N-(phosphonomethyl)iminodiacetic acid substrates produced by other routes than the catalytic liquid phase oxidation of N-(phosphonomethyl)iminodiacetic acid substrates known in the art. The wet cake product is recovered from the solution containing the N-(phosphonomethyl)glycine product.

It is recognized in the art that liquid phase oxidation of N-(phosphonomethyl)iminodiacetic acid substrates can be carried out in batch, semi-batch or continuous reactor systems containing one or more oxidation reaction zones. The oxidation reaction zone may suitably be provided by various reactor configurations including those of back-mixing nature in the liquid phase and optionally also in the gas phase, and those of plug flow nature. Suitable reactor configurations with back mixing characteristics include, for example, stirred tank reactors, jet nozzle loop reactors (also known as Venturi loop reactors) and fluidized bed reactors. Suitable reactor configurations with plug flow characteristics include those with packed or fixed catalyst beds (eg, trickle bed reactors and packed bubble column reactors) and bubbling slurry column reactors. Fluidized bed reactors can also be operated in a manner that exhibits plug flow characteristics. The configuration of the oxidation reactor system, including the multiple oxidation reaction zones, and the oxidation reaction conditions are not critical to the practice of the present invention. Suitable oxidation reactor systems and oxidation reaction conditions for use in the liquid-phase catalytic oxidation of N-(phosphonomethyl)iminodiacetic acid substrates are known in the prior art and are described, for example, by Ebner et al. in US Pat. No. 6,417,133, described by Leiber et al. in US Patent No. 6,586,621, and by Haupfear et al. in International Patent Publication No. WO01/92272 and the corresponding US Patent Publication No. US-2002-0068836-A1 , the entire disclosures of which are incorporated herein by reference.

The method described here has been found to be particularly useful for recovering various N- (Phosphonomethyl)glycine wet cake product. It is important to note, however, that the present invention is not limited to such applications or to use in connection with continuous oxidation reactor systems in general. As is well understood by those skilled in the art, the strategies set forth herein can be ideally used to recover crystalline wet cake products from oxidation reaction solutions produced in various reactor systems, including batch reactor systems.

Generally, in one embodiment, the method of the present invention includes separating the wet cake product from a slurry comprising precipitated product crystals and mother liquor. The product slurry is divided into fractions comprising at least a first fraction and a second fraction. Product crystals are separated from each of the first and second fractions by dewatering in one or more liquid/solid separation devices to produce a first wet cake product and a second wet cake product, respectively.

More specifically, it has been found that the impurity content of the separated wet cake product can be increased by producing at least two wet cake products from a slurry comprising precipitated product crystals and mother liquor such that the second wet cake product has a higher solids content than the first wet cake product. The solids content of a wet cake product is kept below a desired value. Therefore, it is necessary in the practice of this aspect of the invention to have the first and second wet cake products have different solids contents such that a different impurity composition is obtained due to the different amounts of impurity-containing mother liquor in the wet cake. Each wet cake product. For example, the ratio of the solids content of the second wet cake product to the solids content of the first wet cake product is typically at least about 1.1. Preferably, the ratio of the solids content of the second wet cake product to the solids content of the first wet cake product is at least about 1.2 as measured by weight percent solids in each of the first and second wet cake products . More preferably, the ratio of the solids content of the second wet cake product to the solids content of the first wet cake product is at least about 1.25.

According to a preferred embodiment, the solids content of the second wet cake product is preferably at least about 85% by weight solids. More preferably, the second wet cake product has a solids content of from about 90% solids to about 99% solids by weight. Most preferably, the second wet cake product has a solids content of from about 95% solids to about 99% solids by weight. Generally, increasing the solids content of the second wet cake product results in the recovery of a greater amount of the second wet cake product with an acceptable purity. Likewise, it is preferred that the first wet cake product has a solids content of less than about 85% by weight solids. More preferably, the first wet cake product has a solids content of less than about 75% by weight solids. For example, the first wet cake product can have a solids content of from about 70% solids to about 85% solids by weight. It will be appreciated that as the level of impurities in the crystallization feed solution decreases, the product crystal size tends to increase, resulting in more efficient dehydration and higher solids content in the wet cake product.

Although not necessary or critical to the present invention, it is contemplated that the first and second wet cake products can typically be produced using separate liquid/solid separation equipment, preferably separate liquid/solid separation equipment arranged or operated in parallel. In general, any liquid/solid separation device suitable for separating crystalline products from mother liquors can be used in the present invention. However, because of the higher yields and Capacity requirements, preferred embodiments of the invention typically employ liquid/solid separation equipment suitable for press filtration, vacuum filtration and/or centrifugation. For example, preferred liquid/solid separation equipment may include vacuum drums, vacuum flat filters and/or centrifuges. In a particularly preferred embodiment, the product crystals are separated from the first and second slurry fractions by centrifugation, preferably in separate centrifuges, and even more preferably in separate centrifuges operating in parallel. In an especially preferred embodiment, the first wet cake product is separated in a non-porous drum centrifuge, and the second wet cake product is separated in a basket centrifuge (or a storage tank of a basket centrifuge) of. Alternatively, it is contemplated that the product crystals may be separated from the first and second slurry fractions in similar liquid/solid separation equipment and/or under conditions such that initially produced wet cakes have approximately equal solids content. In such embodiments, the wet cake product is produced by blending the mother liquor separated from either the first or second product slurry fractions (i.e., exporting the separated product directly or in a subsequent processing step). The mother liquor to be blended with the wet cake product) makes it possible to obtain the desired solids content ratio in the first and second wet cake products.

A particularly preferred embodiment in which the product crystals are separated from the first and second fractions of the product slurry in separate liquid/solid separation devices operating in parallel is shown in Figure 1 . Feed solution 1 comprising readily crystallizable product is introduced into crystallization stage 3 to produce a crystalline product slurry or thin paste 5 comprising precipitated product crystals and mother liquor. For example, a product slurry containing N-(phosphonomethyl)glycine product crystals and a mother liquor can be vapor-driven from the reaction solution obtained from the catalytic liquid-phase oxidation of the N-(phosphonomethyl)iminodiacetic acid substrate. Evaporative crystallization, adiabatic crystallization or adiabatic crystallization combined with decantation are used for production. An overhead vapor stream 7 is withdrawn from the crystallization stage.

The product slurry 5 is divided into a first fraction 9 and a second fraction 11 . The proportion of product slurry divided into first and second fractions can vary considerably. For example, the first fraction 9 from the slurry 5 may comprise about 20-100%, about 40-60%, or about 50% of the slurry, with the second fraction 11 comprising the remainder of the slurry.

The first slurry fraction 9 is introduced into a first liquid/solid separation device 13, such as a centrifuge, preferably a non-porous drum centrifuge, to produce a first wet cake product 15 and a solids-depleted stream 17 (e.g., centrifugal filtrate), which is typically recycled back into crystallization stage 3. However, at least a portion of solids-depleted stream 17 may optionally be back-mixed with wet cake 15, as shown by the dashed line in FIG. 1, to produce a first wet cake product having an even lower solids content. Additionally, at least a portion of the solids-depleted stream 17 may optionally be back-mixed with the wet cake 15 in subsequent processing steps.

The second product slurry fraction 11 may optionally be introduced to a hydrocyclone 19 (or a storage tank of a hydrocyclone) to form a concentrated second slurry fraction 23 rich in precipitated products and a solids depleted stream twenty one. The concentrated second fraction 23 is introduced to a separator feed tank 25 which feeds a second liquid/solid separation device, preferably a basket centrifuge. Alternatively, the product slurry fraction 11 may be fed directly into the separator feed tank 25 or directly into the second liquid/solid separation device. In the preferred embodiment shown in Figure 1, the concentrated second fraction is introduced into the storage tank of the basket centrifuge. Thus, concentrated second fraction 23 accumulated in separator feed tank 25 is divided into concentrated slurry fractions 27A and 27B, which are introduced into basket centrifuges 29A and 29B, respectively. Basket centrifuges produce wet cake products 31A and 31B respectively, which are blended to form second wet cake product 35 . The basket centrifuge also produces centrates 33A and 33B which are further devoid of precipitated products and can be recycled back to crystallization stage 3 . However, at least a portion of the centrate 33A and/or 33B may optionally be backmixed with the wet cake product 31A, 31B and/or the second wet cake product 35 or mixed with the first wet cake product 15 to produce an even lower The solids content of the wet cake product.

As mentioned above, the liquid/solid separation equipment used to dewater the first and second product slurry fractions 9 and 11 in Figure 1 is preferably a non-porous drum centrifuge and one or more basket centrifuges respectively . When the first wet cake product can contain more water and impurities without affecting product specifications, the combination of non-porous drum centrifuge and vertical basket centrifuge can provide higher solids capacity capacity and at the same time Lower capital and operating costs are required.

In the embodiment shown in FIG. 1 , the second wet cake product 35 will have a lower amount of impurities than the first wet cake product 15 due to the lower amount of entrapped mother liquor in the wet cake product. In addition, the second wet cake product 35 typically has impurity levels below required specifications and has an assay amount of N-(phosphonomethyl)glycine product of at least about 95% by weight (on a dry basis) such that it can be used as The final product is packaged, or used as starting material in subsequent processing steps, for example in the preparation of concentrated liquid or solid salts of N-(phosphonomethyl)glycine for formulation of herbicidal compositions. The obtained first wet cake product 15 may or may not meet applicable purity specifications, but may be used in conjunction with other treatments such as mixing with a higher purity N-(phosphonomethyl)glycine product or recrystallization, A substance or product of acceptable purity is also produced having properties different from the second wet cake product.

The embodiment shown in Figure 1 may be part of a process where stage 3 is the only crystallization step. However, the embodiment shown in FIG. 1 may also be part of a wider process containing other crystallization stages, as described below in relation to FIG. 2 .

In a particularly preferred embodiment, the invention comprises the production of and Various wet cakes containing crystalline N-(phosphonomethyl)glycine product were recovered.

Referring now to FIG. 2, an aqueous feed stream 101 comprising N-(phosphonomethyl)iminodiacetic acid substrate is introduced along with oxygen into an oxidation reactor system 103 comprising one or more oxidation reaction zones, wherein The N-(phosphonomethyl)iminodiacetic acid substrate is oxidatively cleaved in the presence of a suitable catalyst to form an aqueous oxidation reaction solution 105 comprising the N-(phosphonomethyl)glycine product and impurities. In order to reduce the level of impurities in the oxidation reaction solution 105, the catalyst used in the oxidation reaction zone is preferably a heterogeneous catalyst comprising a noble metal supported on a carbon support, for example, as described by Ebner et al. in US Patent No. 6,417,133 described in . The oxidation reaction solution 105 withdrawn from the reactor system 103 is then divided into fractions, one portion 107 (i.e., the primary fraction of the oxidation reaction solution) is introduced into the first crystallizer 111 operated substantially adiabatically and where concentrated (i.e., any heat input to or output from the crystallizer is no greater than about 200 kcal/kg of oxidation reaction solution fed to the crystallizer) to produce precipitated N-(phosphonomethyl base) primary product slurry or paste 113 of glycine product crystals and primary mother liquor. Another portion 109 (i.e., the secondary fraction of the oxidation reaction solution) is introduced into a non-adiabatic heat-driven evaporative crystallizer 125 and concentrated therein to produce crystals comprising precipitated N-(phosphonomethyl)glycine product and The evaporated crystallization slurry or thin paste 126 of the secondary mother liquor (ie, the secondary product slurry).

Suitable operation of adiabatic crystallizer 111 and non-adiabatic crystallizer 125 in the product recovery system shown in Figure 2 is described by Haupfear et al in International Patent Publication No. WO01/92272 and corresponding US Patent Publication No. US-2002- 0068836-A1, the contents of which are incorporated herein by reference. As described in this publication, the adiabatic crystallizer 111 serves three distinct functions, including: rapid evaporation of a portion of the oxidation reaction solution, N-( Crystallization of the phosphonomethyl)glycine product, and subsequent decantation of most of the crystallization mother liquor for recycling to the reactor system. This decanting is also used to concentrate the solids content of the primary product slurry fed to the liquid/solids separation unit to reduce dewatering load and increase dewatering capacity. These functions can be provided integrally in a single adiabatic crystallizer unit or in a combination of these units.

Preferably about 30-85%, more preferably about 50-80%, and even more preferably about 65-75% of the oxidation reaction solution 105 is introduced into the adiabatic crystallizer 111 via stream 107 as a primary fraction, while the remainder is introduced via stream 107. Stream 109 is introduced into a non-adiabatic heat-driven crystallizer 125 as a secondary fraction. The weight ratio of secondary fraction 109 to N-(phosphonomethyl)iminodiacetic acid substrate fed to reactor system 103 is preferably about 0.1-9, more preferably about 0.2-5, even more preferably about 0.25 -2.5. However, the ratio of the oxidation reaction solution 105 introduced into the adiabatic crystallizer 111 and the weight ratio of the secondary fraction 109 to the N-(phosphonomethyl)iminodiacetic acid substrate fed into the reactor system 103 are in the range of It is not critical to the practice of the invention.

Operation of the adiabatic crystallizer 111 produces a vapor 115 withdrawn from the top of the crystallizer (i.e., the adiabatic crystallizer overhead), a decantate (i.e., primary mother liquor) stream 112 withdrawn from the crystallizer, and a stream 112 withdrawn from the crystallizer bottom. A primary crystalline product slurry 113 that is discharged and comprises precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor containing uncrystallized (i.e., dissolved) N-(phosphonomethyl)glycine products and impurities. Preferably, at least a portion (and more preferably all) of the adiabatic crystallizer overhead 115 and/or decantate 112 withdrawn from the adiabatic crystallizer 111 is recycled back into the oxidation reactor system 103 .

Primary crystallization product slurry 113, withdrawn from the bottom of adiabatic crystallizer 111, comprising precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor, is introduced into liquid/solid separation device 117, preferably a basket centrifuge or basket centrifuge to produce a wet cake product 119 and a solids depleted stream 123 (eg, centrate). At least a portion of the solids-depleted stream 123 can be recycled back to the adiabatic crystallizer 111 and/or optionally can be recycled back to the oxidation reactor system 103, as indicated by the dashed line in FIG. 2 . More preferably, wet cake product 119 has a solids content of from about 90% to about 99% by weight as described above.

The feedstock (ie, secondary fraction 109 ) fed to the non-adiabatic crystallizer can be processed in a similar manner as described above for Feedstock Solution 1 in FIG. 1 . In operation of the non-adiabatic evaporative crystallizer 125 , heat is transferred to the secondary fraction 109 to evaporate water (and small molecular impurities such as formaldehyde and formic acid) and form the non-adiabatic crystallizer overhead vapor stream 127 . Precipitation of the N-(phosphonomethyl)glycine product produced an evaporative crystallization sludge comprising the precipitated N-(phosphonomethyl)glycine product and a secondary mother liquor containing dissolved N-(phosphonomethyl)glycine product and impurities. Pulp 126. Slurry 126 is withdrawn from adiabatic evaporative crystallizer 125 and divided into multiple fractions including first fraction 129 and second fraction 131 . The first fraction 129 is introduced into a first liquid/solid separation device 133, preferably a non-porous drum centrifuge, to produce a first fraction wet cake having a solids content of about 70-85% by weight as described above Product 153 and solids depleted stream 134 (eg, centrate). The solids depleted stream 134 is typically recycled back to the non-adiabatic evaporative crystallizer 125 . However, at least a portion of the solids-depleted stream 134 can optionally be back-blended with the wet cake, as shown by the dashed line in FIG. 2, to produce a first fraction wet cake product 153A having an even lower solids content. First fraction wet cake product 153 or 153A is then preferably blended with wet cake product 119 produced from adiabatic crystallizer 111 to produce first wet cake product 121 . However, it should be understood that first fraction wet cake product 153 or 153A and wet cake product 119 may each be further processed without first blending these materials to produce first wet cake product 121 . Additionally, at least a portion of solids-depleted stream 134 may optionally be blended with first fraction wet cake product 153 and wet cake product 119 produced from adiabatic crystallizer 111 to produce first wet cake product 121, as shown in FIG. 2 is shown by the dotted line.

A second fraction 131 of the evaporated product slurry is optionally introduced into a hydrocyclone 135 (or a storage tank of a hydrocyclone) to form a concentrated second fraction rich in precipitated N-(phosphonomethyl)glycine product. Slurry fraction 137 and solids depleted stream 139 . Hydrocyclone solids depleted stream 139 is preferably recycled back to heat driven evaporative crystallizer 125 to achieve further recovery of N-(phosphonomethyl)glycine product. Concentrated second fraction 137 is introduced into separator feed tank 141, which feeds a second liquid/solid separation device, preferably capable of producing 99% by weight solids) basket centrifuge for wet cake product. Alternatively, the second fraction 131 of the evaporated product slurry can be fed directly to the separator feed tank 141 or directly to the second liquid/solid separation device. In the preferred embodiment shown in Figure 2, the concentrated second slurry fraction 137 is introduced into the storage tanks of the basket centrifuges operating in parallel. Thus, the concentrated slurry accumulated in separator feed tank 141 is divided into concentrated slurry fractions 143A and 143B, which are introduced into basket centrifuges 145A and 145B, respectively. The basket centrifuges each produce product wet cakes 149A and 149B respectively, which are blended to form a second wet cake product 151 . The basket centrifuge also produces centrates 147A and 147B, which are further depleted of precipitated products and can be recycled back to the non-adiabatic evaporative crystallizer 125. Alternatively, at least a portion of the centrate 147A, 147B, and/or 134 may be purged from the process if desired to obtain a wet cake product of acceptable purity. It should be understood that, as described herein, the storage tanks of the liquid/solid separation plant are considered to operate in parallel, even if intermittent dehydration cycles in each plant cannot be maintained in phase.

In the operation of the product recovery system shown in Figure 2, it is expected that the concentration of impurities in the primary mother liquor produced in the adiabatic crystallizer system will be lower than in the secondary mother liquor produced in the non-adiabatic evaporative crystallizer system. Impurity concentrations, especially since the overhead to feed ratio of the non-adiabatic crystallizer is significantly lower than the overhead to feed ratio of the adiabatic crystallizer. It is also expected that the second wet cake product 151 will typically have impurity levels meeting specifications and contain at least about 95% by weight N-phosphonomethyl)glycine product (reduced dry calculation). However, the first fraction wet cake product, 153, is not processed further and need not be of acceptable purity due to the increased amount of entrapped mother liquor. By blending the first fraction wet cake product 153 with wet cake product 119 (generally a higher purity material), the overall ratio of impurities to N-(phosphonomethyl)glycine becomes acceptable, and thus further processed A marketable product can be produced from this material. Such further processing may include drying operations to remove excess water to produce a wet cake, or further addition of base neutralization components to produce a suitable N-(phosphonomethyl)glycinate product or formulation of acceptable purity. For example, the N-(phosphonomethyl)glycine product in the first wet cake product 121, or in each of the first fraction wet cake product 153 and the wet cake product 119, can be conventionally used with one or more Base neutralization to prepare the agriculturally acceptable salt of N-(phosphonomethyl)glycine commonly used in glyphosate herbicidal formulations. Examples of agriculturally acceptable salts of N-(phosphonomethyl)glycine include cations selected from alkali metal cations (e.g., potassium and sodium ions), ammonium ions, isopropylammonium ions, tetra-alkylammonium ions , trialkylsulfonium ions, protonated primary amines, protonated secondary amines, and protonated tertiary amines. Thus, the embodiment shown in FIG. 2 can readily produce at least two different products of acceptable purity, a second wet cake product 151 and a product obtained from further processing of the first wet cake product 121, and provides Overall improved process flexibility.

While the embodiment shown in FIG. 2 employing two or more crystallization operations operating in a semi-parallel fashion has been found to be ideal for producing a variety of acceptable wet cake products, depending on the There is a limit to the amount of second wet cake product 151 that can be produced with acceptable purity. In some cases, general washing of the second wet cake product 151 can be used to reduce the concentration of impurities and increase the amount of acceptable material 151 produced. However, in some cases as described below, there is a practical limit to the amount of cake wash that can be used.

As the relative production of the second wet cake product 151 increases, impurities tend to accumulate in the secondary mother liquor of the non-adiabatic crystallizer system to a point where the concentration is high enough to significantly reduce scrubbing efficiency. Elevated impurity concentrations tend to reduce crystal size so that subsequent dehydration operations are hampered and a larger amount of impurity-containing liquid remains entrained in the second wet cake product 151 . Furthermore, it is believed that at higher concentrations some of these impurities may be introduced into the product crystals, reducing cake washing efficiency. These "solid-phase entrapped impurities" or other difficult-to-remove impurities in the second wet cake product 151 require thorough washing of the crystals or other drastic measures such as reslurrying with water or recrystallization to meet typical product requirements. Purity specification. These washes are typically recycled back to the evaporative crystallizer 125 to minimize loss of soluble product. Unfortunately, the washed impurities are also recycled and concentrated in the evaporative crystallizer, exacerbating the solid-phase impurity entrapment problem and also concentrating corrosive compounds, exacerbating the structural material damage problem, and ultimately causing the centrate to clear ( For example, 147A, 147B and/or 134). Impurities not removed in the centrate will end up in the second wet cake product 151, resulting in a disproportionate redistribution of impurities to this portion of the product. In any event, as the amount of wash water increases, it becomes impractical and cost-effective to evaporate the recycled wash liquor in the evaporative crystallizer without increasing the costs associated with product purity and overall process efficiency. In the case of other problems, it is also not possible to recycle these washing liquids to other operations in the process or to remove them from the process.

According to other embodiments of the invention, it has been found that if the wet cake product produced is the result of blending material from one of these crystallization operations with material from the other crystallization operation and preferably when the material is obtained from an adiabatic crystallizer system When the medium is transferred to a non-adiabatic crystallizer system, then many of the limitations described above can be overcome, increasing the process flexibility obtained and achieving better impurity control. This increased process flexibility becomes particularly useful when a higher fraction of the total product is directed to the production of the second wet cake product 151 . More specifically, it has been found that impurities in the wet cake product produced by the method of the present invention can be kept below desired levels by: , secondary) the net transfer of impurities contained in the mother liquor fraction to another of the first (i.e., adiabatic) and second (i.e., non-adiabatic evaporation) crystallization operations; and/or net transfer of impurities contained in the second mother liquor fraction to another of the first and second liquid/solid separation steps associated with the other of the first and second crystallization operations; (iii) net transfer of the lower impurity content wet cake product obtained from one of the first and second liquid/solid separation steps to the other of the first and second crystallization operations; The lower impurity content wet cake product obtained in one of the first and second liquid/solid separation steps is net transferred to the first and second liquid/solids associated with the other of the first and second crystallization operations In another of the separation steps; (v) net transfer of the lower impurity content product slurry or paste obtained in one of the first and second crystallization operations to the first and second crystallization operations (vi) net transfer of the product slurry or thin paste with lower impurity content obtained in one of the first and second crystallization operations to the other of the first and second crystallization operations In the other of the first and second liquid/solid separation steps involved in one operation; or any combination of (i), (ii), (iii), (iv), (v) and/or (vi) .

A preferred embodiment of the process of the present invention for the production and recovery of two wet cake products comprising crystalline N-(phosphonomethyl)glycine from an oxidation reaction solution comprising dissolved N-(phosphonomethyl)glycine product and impurities is shown in Figure 3. Similar to the process shown and described in Figure 2, the product recovery system of Figure 3 uses a combination of a semi-parallel operating adiabatic crystallizer system and a non-adiabatic heat-driven evaporative crystallizer. However, according to this embodiment, the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is achieved by net transfer of the primary product slurry or paste from the adiabatic crystallizer system and combining it with the The admixture of the N-(phosphonomethyl)glycine product contained in the secondary fraction of the oxidation reaction solution was controlled. More specifically, in the embodiment shown in Figure 3, the impurity profile in the wet cake product of crystalline N-(phosphonomethyl)glycine was achieved by net transfer of the primary product slurry to the second stage of the evaporative crystallizer. Controlled in product slurry or thin paste.

Many of the various streams shown in FIG. 3 are similar to those described above for FIG. 2 . Referring now to FIG. 3, an aqueous feed stream 101 comprising N-(phosphonomethyl)iminodiacetic acid substrate is introduced along with oxygen into an oxidation reactor system 103 comprising one or more oxidation reaction zones, wherein The N-(phosphonomethyl)iminodiacetic acid substrate is oxidatively cleaved in the presence of a catalyst to form an aqueous oxidation reaction solution 105 . The oxidation reaction solution 105 withdrawn from the reactor system 103 is then divided into fractions, one portion 107 (i.e., the primary fraction of the oxidation reaction solution) is introduced into an adiabatic crystallizer 111 to produce N-(phosphine Primary product slurry 113 of acylmethyl)glycine product crystals and primary mother liquor. Another portion 109 (i.e., the secondary fraction of the oxidation reaction solution) is introduced into a non-adiabatic heat-driven evaporative crystallizer 125 to produce crystals comprising precipitated N-(phosphonomethyl)glycine product and a secondary mother liquor The evaporated crystallization slurry 126 (ie, secondary product slurry).

Operation of the adiabatic crystallizer 111 produces a vapor 115 withdrawn from the top of the crystallizer (i.e., the adiabatic crystallizer overhead), a decantate (i.e., primary mother liquor) stream 112 withdrawn from the crystallizer, and a stream 112 withdrawn from the crystallizer bottom. A primary crystalline product slurry 113 is discharged and comprises precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor. Preferably, at least a portion (and more preferably all) of the adiabatic crystallizer overhead 115 and/or decantate 112 withdrawn from the adiabatic crystallizer 111 is recycled back into the oxidation reactor system 103 .

The primary crystallization product slurry 113 is divided into two fractions 113A and 113B. Portion 113A is introduced into liquid/solids separation apparatus 117, preferably a basket centrifuge or storage tank of a basket centrifuge, producing a wet cake product 119 and a solids-depleted stream 123 (eg, centrate). At least a portion of the solids-depleted stream 123 can be recycled back to the adiabatic crystallizer 111 and/or optionally can be recycled back to the oxidation reactor system 103, as indicated by the dashed line in FIG. 3 . More preferably, wet cake product 119 has a solids content of from about 90% to about 99% by weight as described above. Portion 113B is transferred to separator feed tank 141 as described below.

In operation of the non-adiabatic evaporative crystallizer 125 , heat is transferred to the secondary fraction 109 to evaporate water (and small molecular impurities such as formaldehyde and formic acid) and form the non-adiabatic crystallizer overhead vapor stream 127 . Precipitation of the N-(phosphonomethyl)glycine product produces an evaporative crystallization slurry 126 comprising the precipitated crystalline N-(phosphonomethyl)glycine product and secondary mother liquor. Slurry 126 is withdrawn from adiabatic evaporative crystallizer 125 and divided into multiple fractions including first fraction 129 and second fraction 131 . The first fraction 129 is introduced into a first liquid/solid separation device 133, preferably a non-porous drum centrifuge, to produce a first fraction wet cake having a solids content of about 70-85% by weight as described above Product 153 and solids depleted stream 134 (eg, centrate). The solids depleted stream 134 is typically recycled back to the non-adiabatic evaporative crystallizer 125 . However, at least a portion of the solids-depleted stream 134 can optionally be back-blended with the wet cake, as shown by the dashed line in FIG. 3, to produce a first fraction wet cake product 153A having an even lower solids content. First fraction wet cake product 153 or 153A is then preferably blended with wet cake product 119 produced from adiabatic crystallizer 111 as described above to produce first wet cake product 121 .

A second fraction 131 of the evaporated product slurry is optionally introduced into a hydrocyclone 135 (or a storage tank of a hydrocyclone) to form a concentrated second fraction rich in precipitated N-(phosphonomethyl)glycine product. Slurry fraction 137 and solids depleted stream 139 . Hydrocyclone solids depleted stream 139 is preferably recycled back to heat driven evaporative crystallizer 125 to achieve further recovery of N-(phosphonomethyl)glycine product. Concentrated second fraction 137 is introduced into separator feed tank 141 and blended with portion 113B of primary product slurry to form secondary fraction product mixture 143 . Secondary fraction product mixture 143 is supplied to liquid/solid separation equipment, preferably a basket type capable of producing a wet cake product with a relatively high solids content (typically from at least about 85% to about 99% by weight solids). in the centrifuge. Alternatively, the second fraction 131 of the evaporated product slurry can be fed directly to the separator feed tank 141, or both the second fraction 131 of the evaporated product slurry and the portion 113B of the primary product slurry can be fed directly to the second fraction of the evaporated product slurry. Two liquid/solid separation equipment. In the preferred embodiment shown in Figure 3, the secondary fraction product mixture 143 is introduced into the storage tanks of the basket centrifuges operating in parallel. Thus, secondary fraction product mixture 143 from separator feed tank 141 is split into product mixture fractions 143A and 143B, which are introduced into basket centrifuges 145A and 145B, respectively. The basket centrifuges each produce product wet cakes 149A and 149B respectively, which are blended to form a second wet cake product 151 . The basket centrifuge also produces centrates 147A and 147B, which are further depleted of precipitated products and can be recycled back to the non-adiabatic evaporative crystallizer 125. Alternatively, at least a portion of the centrate 147A, 147B, and/or 134 may be purged from the process if desired to obtain a wet cake product of acceptable purity.

When cake washing of the second wet cake product 151 becomes impractical, operation of the embodiment shown in FIG. There are limitations to the production of cake product 151 (relative to total system production). The solid and liquid phase impurities in portion 113B of primary product slurry 113 are significantly lower than those in concentrated second slurry fraction 137 . Blending of these streams in 143 at higher than minimum ratios reduces the average impurity levels in the solid and/or liquid phases, allowing for reduced washout and eventual elimination of the second wet cake product 151 . The obtained second wet cake product 151 may carry a larger amount of impurities from the evaporative crystallizer than would otherwise be the case, resulting in a better impurity balance between wet cake products 121 and 151 . This occurs despite the partial dilution of liquid phase impurities in the second product fraction mixture 143 due to the lower impurity content in the portion 113B of the primary product slurry 143 . In typical practice, desirable results are obtained when about 10-30% by weight of the primary product slurry 113 is transferred to the secondary fraction product mixture 143 . It is to be understood, however, that the exact ratios may vary widely without departing from the scope of the invention, and those skilled in the art will appreciate that the exact ratios depend on various parameters, including The composition of the secondary product slurry 126.

Another preferred embodiment for the production and recovery of two wet cake products comprising crystalline N-(phosphonomethyl)glycine from an oxidation reaction solution comprising dissolved N-(phosphonomethyl)glycine product and impurities is shown in Figure 4 -6 in. Similar to the processes shown and described in Figures 2 and 3, the product recovery systems of these additional embodiments use a combination of a semi-parallel operating adiabatic crystallizer system and a non-adiabatic heat driven evaporative crystallizer. Thus, many of the various streams shown in Figures 4-6 are similar to those described above for Figures 2 and 3 .

The process embodiment illustrated in FIG. 4 is a variation of the process described in FIG. 3, wherein the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is likewise determined by making the primary product slurry or thin paste Net transfer from the adiabatic crystallizer system and its admixture with the N-(phosphonomethyl)glycine product contained in the secondary fraction of the oxidation reaction solution is controlled. However, in the process shown in Figure 4, the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is achieved by net transfer of the primary product slurry or thin paste from the adiabatic crystallizer system to the evaporating controlled in the crystallizer.

Referring now to FIG. 4, an aqueous feed stream 101 comprising N-(phosphonomethyl)iminodiacetic acid substrate is introduced along with oxygen into an oxidation reactor system 103 comprising one or more oxidation reaction zones, wherein The N-(phosphonomethyl)iminodiacetic acid substrate is oxidatively cleaved in the presence of a catalyst to form an aqueous oxidation reaction solution 105 . The oxidation reaction solution 105 withdrawn from the reactor system 103 is then divided into fractions, one portion 107 (i.e., the primary fraction of the oxidation reaction solution) is introduced into an adiabatic crystallizer 111 to produce N-(phosphine Primary product slurry 113 of acylmethyl)glycine product crystals and primary mother liquor. Another portion 109 (i.e., the secondary fraction of the oxidation reaction solution) is introduced into a non-adiabatic, heat-driven evaporative crystallizer 125 to produce a fraction comprising precipitated N-(phosphonomethyl)glycine product crystals and a secondary mother liquor. The crystallization slurry 126 (ie, secondary product slurry) is evaporated.

Operation of the adiabatic crystallizer 111 produces a vapor 115 withdrawn from the top of the crystallizer (i.e., the adiabatic crystallizer overhead), a decantate (i.e., primary mother liquor) stream 112 withdrawn from the crystallizer, and a stream 112 withdrawn from the crystallizer bottom. A primary crystalline product slurry 113 is discharged and comprises precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor. Preferably, at least a portion (and more preferably all) of the adiabatic crystallizer overhead 115 and/or decantate 112 withdrawn from the adiabatic crystallizer 111 is recycled back into the oxidation reactor system 103 .

The primary crystallization product slurry 113 is divided into two fractions 113A and 113B. Portion 113A is introduced into liquid/solids separation apparatus 117, preferably a basket centrifuge or storage tank of a basket centrifuge, producing a wet cake product 119 and a solids-depleted stream 123 (eg, centrate). At least a portion of the solids-depleted stream 123 can be recycled back to the adiabatic crystallizer 111 and/or optionally can be recycled back to the oxidation reactor system 103, as indicated by the dashed line in FIG. 4 . More preferably, wet cake product 119 has a solids content of from about 90% to about 99% by weight as described above.

Portion 113B of primary product slurry 113 is blended with secondary fraction 109 of the oxidation reaction solution to form evaporative crystallizer feed mixture, which is transferred to evaporative crystallizer 125 for crystallization of N-(phosphonomethyl) Precipitation of glycine product. Although not necessary or critical to the invention, it is contemplated that fraction 113B may be introduced directly into evaporative crystallizer 125 or may be premixed with secondary fraction 109, for example in a holding tank (not shown). In either case, heat is transferred to the resulting evaporative crystallizer feed mixture in the non-adiabatic evaporative crystallizer 125 to evaporate water (and small molecule impurities such as formaldehyde and formic acid) and form a non-adiabatic crystallizer overhead vapor stream 127. Precipitation of the N-(phosphonomethyl)glycine product produces an evaporative crystallization slurry 126 comprising the precipitated crystalline N-(phosphonomethyl)glycine product and secondary mother liquor. Slurry 126 is withdrawn from adiabatic evaporative crystallizer 125 and divided into multiple fractions including first fraction 129 and second fraction 131 . The first fraction 129 is introduced into a first liquid/solid separation device 133, preferably a non-porous drum centrifuge, to produce a first fraction wet cake having a solids content of about 70-85% by weight as described above Product 153 and solids depleted stream 134 (eg, centrate). The solids depleted stream 134 is typically recycled back to the adiabatic evaporative crystallizer 125 . However, at least a portion of the solids-depleted stream 134 can optionally be back-mixed with the wet cake, as shown by the dashed line in FIG. 4, to produce a first fraction wet cake product 153A having an even lower solids content. First fraction wet cake product 153 or 153A is then preferably blended with wet cake product 119 produced from adiabatic crystallizer 111 as described above to produce first wet cake product 121 .

A second fraction 131 of the evaporated product slurry is optionally introduced into a hydrocyclone 135 (or a storage tank of a hydrocyclone) to form a concentrated second fraction rich in precipitated N-(phosphonomethyl)glycine product. Slurry fraction 137 and solids depleted stream 139 . Hydrocyclone solids depleted stream 139 is preferably recycled back to heat driven evaporative crystallizer 125 to achieve further recovery of N-(phosphonomethyl)glycine product. Concentrated second fraction 137 is introduced into separator feed tank 141, which feeds a second liquid/solid separation device, preferably capable of producing Basket centrifuge for wet cake product of solids). Alternatively, the second fraction 131 of the evaporated product slurry can be fed directly to the separator feed tank 141 or directly to the second liquid/solid separation device. In the preferred embodiment shown in Figure 4, the concentrated second slurry fraction 137 is introduced into a series of basket centrifuges operating in parallel. Thus, the concentrated slurry accumulated in separator feed tank 141 is divided into concentrated slurry fractions 143A and 143B, which are introduced into basket centrifuges 145A and 145B, respectively. These basket centrifuges each produce product wet cakes 149A and 149B respectively, which are blended to form a second product wet cake 151 . The basket centrifuge also produces centrates 147A and 147B, which are further depleted of precipitated products and can be recycled back to the non-adiabatic evaporative crystallizer 125. Alternatively, at least a portion of the centrate 147A, 147B, and/or 134 may be purged from the process if desired to obtain a wet cake product of acceptable purity.

Without wishing to be bound by a particular theory, it is believed that the transfer of portion 113B of primary product slurry 113 to the evaporative crystallizer will favorably affect the transfer of N-(phosphonomethyl)glycine product crystals from the secondary fraction 109 of the oxidation reaction solution. Precipitation in , so that fewer impurities and better crystal size distribution can be obtained. More specifically, portion 113B of the adiabatic primary product slurry generally contains large product crystals of high purity. Thus, transfer of portion 113B to the evaporative crystallizer effectively "seeds" the crystallizer to promote crystal growth such that less impurities are introduced into the crystal structure. In any event, those skilled in the art will appreciate that employing any crystal growth that introduces purer crystals from section 113B will enhance the overall purity profile of the product slurry produced from the evaporative crystallization operation.

In practice, the proportion of primary product slurry 113 transferred to the diadiabatic evaporative crystallizer 125 can vary widely without departing from the scope of the invention and the advantageous results obtained.

Another preferred embodiment of the invention for the production and recovery of two wet cake products comprising crystalline N-(phosphonomethyl)glycine product from an oxidation reaction solution comprising dissolved N-(phosphonomethyl)glycine and impurities shown in Figure 5. According to this additional embodiment, the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is obtained by converting the N-(phosphonomethyl)glycine product crystals contained in the first wet cake product from The net transfer in the adiabatic crystallizer system is controlled by admixing the crystals with the N-(phosphonomethyl)glycine product contained in the secondary fraction of the oxidation reaction solution. More specifically, in the embodiment shown in Figure 5, the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product was obtained by separating the N-(phosphonomethyl)glycine product crystals from the Controlled by the net transfer of the wet cake product to the secondary product slurry or paste of the evaporative crystallizer.

Referring now to FIG. 5, an aqueous feed stream 101 comprising N-(phosphonomethyl)iminodiacetic acid substrate is introduced along with oxygen into an oxidation reactor system 103 comprising one or more oxidation reaction zones, wherein The N-(phosphonomethyl)iminodiacetic acid substrate is oxidatively cleaved in the presence of a catalyst to form an oxidation reaction solution 105 . The oxidation reaction solution 105 withdrawn from the reactor system 103 is then divided into fractions, one portion 107 (i.e., the primary fraction of the oxidation reaction solution) is introduced into an adiabatic crystallizer 111 to produce N-(phosphine Primary product slurry 113 of acylmethyl)glycine product crystals and primary mother liquor. Another portion 109 (i.e., the secondary fraction of the oxidation reaction solution) is introduced into a non-adiabatic heat-driven evaporative crystallizer 125 to produce crystals comprising precipitated N-(phosphonomethyl)glycine product and a secondary mother liquor The evaporated crystallization slurry 126 (ie, secondary product slurry).

Operation of the adiabatic crystallizer 111 produces a vapor 115 withdrawn from the top of the crystallizer (i.e., the adiabatic crystallizer overhead), a decantate (i.e., primary mother liquor) stream 112 withdrawn from the crystallizer, and a stream 112 withdrawn from the crystallizer bottom. A primary crystalline product slurry 113 is discharged and comprises precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor. Preferably, at least a portion (and more preferably all) of the adiabatic crystallizer overhead 115 and/or decantate 112 withdrawn from the adiabatic crystallizer 111 is recycled back into the oxidation reactor system 103 .

The primary crystallization product slurry 113 withdrawn from the bottom of the crystallizer, comprising precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor, is introduced into a liquid/solid separation device 117, preferably a basket centrifuge or basket centrifuge to produce a primary wet cake product 119 and a solids depleted stream 123 (eg, centrate). At least a portion of the solids-depleted stream 123 can be recycled back to the adiabatic crystallizer 111 and/or optionally can be recycled back to the oxidation reactor system, as indicated by the dashed line in FIG. 5 . Preferably, the primary wet cake product 119 has a solids content of from about 90% to about 99% by weight as described above. As described further below, at least a portion 119B of primary wet cake 119 is transferred to separator feed tank 141 for blending with the second fraction product slurry produced in the evaporative crystallization operation. Preferably, another portion 119A of the primary wet cake 119 is stored for inclusion in the first wet cake product 121 .

In operation of the non-adiabatic evaporative crystallizer, heat is transferred to the secondary fraction 109 to evaporate water (and small molecular impurities such as formaldehyde and formic acid) and form the non-adiabatic crystallizer overhead vapor stream 127 . Precipitation of the N-(phosphonomethyl)glycine product produces an evaporative crystallization slurry 126 comprising precipitated crystalline N-(phosphonomethyl)glycine product and secondary mother liquor. Slurry 126 is withdrawn from adiabatic evaporative crystallizer 125 and divided into multiple fractions including first fraction 129 and second fraction 131 . The first fraction 129 is introduced into a first liquid/solid separation device 133, preferably a non-porous drum centrifuge, to produce a first fraction wet cake having a solids content of about 70-85% by weight as described above Product 153 and solids depleted stream 134 (eg, centrate). The solids depleted stream 134 is typically recycled back to the non-adiabatic evaporative crystallizer 125 . However, at least a portion of the solids-depleted stream 134 may optionally be back-blended with the wet cake, as shown by the dashed line in FIG. 5, to produce a first fraction wet cake product 153A having an even lower solids content. First fraction wet cake product 153 or 153A is then preferably blended with portion 119A of wet cake product 119 produced from adiabatic crystallizer 111 to produce first wet cake product 121 .

A second fraction 131 of the evaporated product slurry is optionally introduced into a hydrocyclone 135 (or a storage tank of a hydrocyclone) to form a concentrated second fraction rich in precipitated N-(phosphonomethyl)glycine product. Slurry fraction 137 and solids depleted stream 139 . Hydrocyclone solids depleted stream 139 is preferably recycled back to heat driven evaporative crystallizer 125 to achieve further recovery of N-(phosphonomethyl)glycine product. Concentrated second fraction 137 is introduced into separator feed tank 141 and blended with portion 119B of wet cake produced in the adiabatic crystallization operation as described above to form secondary fraction product mixture 143 . Secondary fraction product mixture 143 is supplied to a second liquid/solids separation device, preferably to one capable of producing a wet cake product having a higher solids content (typically from at least about 85% to about 99% by weight solids). in a basket centrifuge. Alternatively, the second fraction 131 of the evaporated product slurry may be fed directly to the separator feed tank 141, or both the second fraction 131 of the evaporated product slurry and the portion 119B of the wet cake produced in the adiabatic crystallization operation Can be added directly to the second liquid/solid separation device. In the preferred embodiment shown in Figure 5, the secondary fraction product mixture 143 is introduced into the storage tanks of the basket centrifuges operating in parallel. Thus, secondary fraction product mixture 143 from separator feed tank 141 is divided into product mixture fractions 143A and 143B, which are introduced into basket centrifuges 145A and 145B, respectively. These basket centrifuges each produce product wet cakes 149A and 149B respectively, which are blended to form a second wet cake product 151 . The basket centrifuge also produces centrates 147A and 147B, which are further depleted of precipitated products and can be recycled back to the non-adiabatic evaporative crystallizer 125. Alternatively, at least a portion of the centrate 147A, 147B, and/or 134 may be purged from the process if desired to obtain a wet cake product of acceptable purity.

Compared to Figure 3, the admixture of the adiabatic wet cake (rather than the adiabatic slurry) in the secondary fraction product mixture 143 allows higher levels of liquid phase impurities to be carried over by the combined solids stream, resulting in a The wet cake product 121 differs in the improvement in impurity profile. This procedure also reduces the evaporative load in the evaporative crystallizer 125 by reducing the amount of water flowing into the evaporative crystallizer system.

In an additional method embodiment of the present invention, wherein the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product is obtained by converting the N-(phosphonomethyl)glycine contained in the first wet cake product to The net transfer of glycine product crystals from the adiabatic crystallizer system and the admixture of the crystals with the N-(phosphonomethyl)glycine product contained in the secondary fraction of the oxidation reaction solution is controlled, as shown in FIG. The process shown was modified such that the N-(phosphonomethyl)glycine product crystals from the first wet cake product were transferred to an evaporative crystallizer. That is, portion 119B of primary wet cake 119 is blended with secondary fraction 109 of the oxidation reaction solution to form evaporative crystallizer feed mixture, which is transferred to evaporative crystallizer 125 for crystallization of N-(phosphonomethyl) Precipitation of glycine product. Although not necessary or critical to the invention, it is contemplated that fraction 119B may be introduced directly into evaporative crystallizer 125 or may be premixed with secondary fraction 109, for example in a holding tank.

In practice, the proportion of adiabatic wet cake 119 transferred to secondary fraction product mixture 143 and/or to evaporative crystallizer 125 may vary widely without departing from the scope of the invention and the resulting advantageous results.

In yet another alternative embodiment of the process shown in FIG. 5, instead of admixing the adiabatic wet cake 119B in the secondary fraction product mixture 143 and/or introducing it to the evaporative crystallizer 125, the adiabatic wet cake may be mixed with The second wet cake product 151 is blended and directly physically mixed to obtain a blended wet cake product with acceptable purity.

Yet another embodiment of the inventive process for the production and recovery of two wet cake products comprising crystalline N-(phosphonomethyl)glycine product from an oxidation reaction solution comprising dissolved N-(phosphonomethyl)glycine product and impurities The scheme is shown in Figure 6. In this embodiment, the impurity profile in the crystalline N-(phosphonomethyl)glycine wet cake product can be obtained by net transfer of impurities contained in one of the first and second mother liquor fractions to control among: (i) the other of the first and second crystallization operations; (ii) the other of the first and second liquid/solid separation steps; (iii) the first and second Another product in the wet cake product; or any combination of (i), (ii) and/or (iii).

Referring now to FIG. 6, an aqueous feed stream 101 comprising N-(phosphonomethyl)iminodiacetic acid substrate is introduced along with oxygen into an oxidation reactor system 103 comprising one or more oxidation reaction zones, wherein The N-(phosphonomethyl)iminodiacetic acid substrate is oxidatively cleaved in the presence of a catalyst to form an oxidation reaction solution 105 . The oxidation reaction solution 105 withdrawn from the reactor system 103 is then divided into fractions, one portion 107 (i.e., the primary fraction of the oxidation reaction solution) is introduced into an adiabatic crystallizer 111 to produce N-(phosphine Primary product slurry 113 of acylmethyl)glycine product crystals and primary mother liquor. Another portion 109 (i.e., the secondary fraction of the oxidation reaction solution) is introduced into a non-adiabatic heat-driven evaporative crystallizer 125 to produce crystals comprising precipitated N-(phosphonomethyl)glycine product and a secondary mother liquor The evaporated crystallization slurry 126 (ie, secondary product slurry).

Operation of the adiabatic crystallizer 111 produces a vapor 115 withdrawn from the top of the crystallizer (i.e., the adiabatic crystallizer overhead), a decantate (i.e., primary mother liquor) stream 112 withdrawn from the crystallizer, and a stream 112 withdrawn from the crystallizer bottom. A primary crystalline product slurry 113 is discharged and comprises precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor. Preferably, at least a portion (and more preferably all) of the adiabatic crystallizer overhead 115 and/or decantate 112 withdrawn from the adiabatic crystallizer 111 is recycled back into the oxidation reactor system 103 .

The primary crystallization product slurry 113 containing precipitated crystalline N-(phosphonomethyl)glycine product and primary mother liquor withdrawn from the bottom of the adiabatic crystallizer is introduced into a liquid/solid separation device 117, preferably a basket centrifuge or basket centrifuge The tank section of the machine to produce a wet cake product 119 and a solids depleted stream 123 (eg, centrate). At least a portion of the solids-depleted stream 123 can be recycled back to the adiabatic crystallizer 111 and/or optionally can be recycled back to the oxidation reactor system 103, as indicated by the dashed line in FIG. 6 . More preferably, wet cake product 119 has a solids content of from about 90% to about 99% by weight as described above.

In operation of the non-adiabatic evaporative crystallizer 125 , heat is transferred to the secondary fraction 109 to evaporate water (and small molecular impurities such as formaldehyde and formic acid) and form the non-adiabatic crystallizer overhead vapor stream 127 . Precipitation of the N-(phosphonomethyl)glycine product produces an evaporative crystallization slurry 126 comprising precipitated crystalline N-(phosphonomethyl)glycine product and secondary mother liquor. Slurry 126 is withdrawn from adiabatic evaporative crystallizer 125 and divided into multiple fractions including first fraction 129 and second fraction 131 . The first fraction 129 is introduced into a first liquid/solid separation device 133, preferably a non-porous drum centrifuge, to produce a first fraction wet cake having a solids content of about 70-85% by weight as described above Product 153 and solids depleted stream 134 (eg, centrate). The solids depleted stream is usually recycled back to the non-adiabatic evaporative crystallizer. However, at least a portion of the solids-depleted stream 134 can optionally be back-mixed with the wet cake, as shown by the dashed line in FIG. 6, to produce a first fraction wet cake product 153A having an even lower solids content. First fraction wet cake product 153 or 153A is then preferably blended with wet cake product 119 produced from the adiabatic crystallizer to produce first wet cake product 121 .

A second fraction 131 of the evaporated product slurry is optionally introduced into a hydrocyclone 135 (or a storage tank of a hydrocyclone) to form a concentrated second fraction rich in precipitated N-(phosphonomethyl)glycine product. Slurry fraction 137 and solids depleted stream 139 . Hydrocyclone solids depleted stream 139 is preferably recycled back to heat driven evaporative crystallizer 125 to achieve further recovery of N-(phosphonomethyl)glycine product. Concentrated second fraction 137 is introduced into separator feed tank 141, which feeds liquid/solid separation equipment, preferably capable of producing Basket centrifuge for wet cake product of solids). In the preferred embodiment shown in Figure 6, the concentrated second slurry fraction 137 is introduced into the storage tanks of the basket centrifuges operating in parallel. Thus, the concentrated slurry accumulated in separator feed tank 141 is divided into concentrated slurry fractions 143A and 143B, which are introduced into basket centrifuges 145A and 145B, respectively. These basket centrifuges each produce product wet cakes 149A and 149B respectively, which are blended to form a second wet cake product 151 . The basket centrifuge also produces centrates 147A and 147B, which are further depleted of precipitated products and can be recycled back to the non-adiabatic evaporative crystallizer 125. Alternatively, at least a portion of the centrate 147A, 147B, and/or 134 may be purged from the process if desired to obtain a wet cake product of acceptable purity.

As shown in Figure 6, at least some options for controlling the impurity profile from the net transfer of impurities contained in the mother liquor may include, but are not limited to: primary mother liquor from adiabatic crystallization (e.g., decant 112 and/or solid depleted feed Stream 123) is transferred to evaporative crystallization operation 125; Centrate 147A and/or 147B is transferred to first wet cake product 121; Centrate 147A and/or 147B is transferred in the adiabatic crystallizer 111; And/or centrate 147A and/or Or 147B is transferred to primary product slurry 113.

The N-(phosphonomethyl)glycine product crystals produced in the adiabatic crystallizer system can be expected to become larger. This provides a material with good handling characteristics when blended with wet cake from a non-adiabatic crystallizer system. However, blended wet cakes may not allow much entrapped liquid. It is therefore desirable to grind the adiabatic crystals to smaller crystal sizes to obtain a more uniform crystal size distribution in the blended material or to ensure the proper amount of liquid entrapped by the blended wet cake for impurity balance reasons.

Example

The following examples are provided merely to further illustrate and explain the present invention. Therefore, the invention should not be limited to any details in these examples.

Example 1

A sample of the N-(phosphonomethyl)glycine wet cake was analyzed and followed up. The wet cake was obtained from the non-adiabatic evaporative crystallizer stage used to dewater the product slurry obtained from the catalytic oxidation of N-(phosphonomethyl)iminodiacetic acid and subjected to a subsequent centrifuge wash cycle. Analysis of impurities in dried samples, namely: formaldehyde, formic acid, N-methyl-N-(phosphonomethyl)glycine (NMG), aminomethylphosphonic acid (AMPA), methylaminomethylphosphonic acid (MAMPA) , iminodiacetic acid (IDA), glycine, iminobis-(methylene)-bis-phosphonic acid (iminobis) and N-(phosphonomethyl)iminodiacetic acid (GI) and N-(phosphono Methyl) glycine content.

The sample was then divided into 3 separate fractions of equal weight, and each of these was reslurried in room temperature water in three different mass ratios, namely 3:1, 7:1 and 15.67:1 water ratio to dry solids. These ratios were 1-2 orders of magnitude higher than typical water displacement ratios in the centrifuge wash step, but were not sufficient to completely dissolve the solids. After a period of time, solid samples were filtered, dried, and reanalyzed.

The purpose of the test is to find impurities that can be washed out from the solid and "occluded" as solid phase impurities. Table 1 below shows each residual solid phase impurity that cannot be washed out by the re-pulp water wash. Other impurities in the wet cake are believed to be washed out during re-pulping. The unit of the data is residual ppm impurity per weight % of N-(phosphonomethyl)glycine (Gly) in the solid phase. Only a minimal increase in purity can be achieved by this method.

Table 1 water/solid ratio GI/Gly ratio ppm% Iminobis/Gly ratio ppm% MAMPA/Gly ratio ppm% AMPA/Gly ratio ppm% IDA/Gly ratio ppm% Glycine/Gly ratio ppm% 0 21.4 110.6 46.9 87.0 22.5 13.8 3:1 20.6 98.1 41.7 76.5 16.5 9.5 7:1 20.7 97.4 41.3 75.2 17.6 9.4 15.67:1 20.9 94.9 41.9 72.7 16.8 8.9

The above solid phase impurities account for 256.1 ppm/per weight% N-(phosphonomethyl)glycine to 302.2 ppm/per weight% N-(phosphonomethyl)glycine in the solid phase. To convert these values to weight percent impurities in the dry wet cake, divide the sum of the values in any row in Table 1 by 10,000 (this is defined as X), and divide the resulting value by 1-X. Performing this arithmetic calculation has shown that there is a 3.12 wt% impurity level in the dried wet cake prior to aqueous repulping and a 2.63 wt% impurity level remains after extensive washing. It should be understood that this implies an N-(phosphonomethyl)glycine content of 96.9-97.4% by weight in the wet cake in this example.

Example 2

Experiments were performed using a system similar to that described in Example 3 to produce and recover N-(phosphonomethyl)glycine wet cake product. Different proportions 113B of the primary product slurry 113 from the adiabatic crystallizer and a fraction 137 of the evaporative crystallization slurry 126 (i.e., secondary product slurry) from the evaporative crystallizer are in the evaporative centrifuge feed tank 141 Blend. During this experiment, the ratio of primary fraction 107 to oxidation reaction solution 105 averaged about 0.79, while the concentration of N-(phosphonomethyl)glycine dissolved in solution 105 averaged about 9% by weight. The solids content in the primary product slurry 113 was maintained at about 25% by weight, while the solids content in the secondary product slurry 126 was maintained at about 11% by weight.

During the course of the experiment, the mass ratio of solids in fraction 113B from primary product slurry to combined solids in 143 was varied from 0 to about 0.40 in increments of about 0.10. Initially, the secondary product was added to the non-porous drum centrifuge 133 before the material from the primary product slurry 113 from the adiabatic crystallizer was blended with the fraction 137 of the secondary product slurry from the evaporative crystallizer Fraction 129 of the slurry averaged about 37% by weight, but increased to about 55% by weight at the end of the experiment while still achieving the same wet cake yield relative to the total yield (i.e., about 15% to about 16%). At each mass ratio of solids in fraction 113B from primary product slurry to combined solids in 143, the amount of centrifuge wash water will be reduced until N-(phosphonomethyl Base) Glycine purity matches the purity value of the previous ratio. A ratio was eventually reached when the water wash was completely removed, but the N-(phosphonomethyl)glycine assay of the combined wet cakes 149A and 149B exceeded that in the primary product slurry 113 from the adiabatic crystallizer. The value obtained before blending with fraction 137 of the secondary product slurry from the evaporative crystallizer. In the combined wet cakes 149A and 149B, the N-(phosphonomethyl)glycine assay would be 95.9-96.4% by weight (on a dry basis).

Example 3

A process material balance model was created and used to simulate and compare the product recovery systems shown in Figures 2, 3 and 5. All model simulations were made with the following assumptions and input values.

The system is operated at steady state with the same base addition of N-(phosphonomethyl)iminodiacetic acid (GI) as in aqueous feed stream 101 supplied to oxidation reactor system 103 . The N-(phosphonomethyl)glycine (Gly) concentration was kept constant at 9.1% by weight in the reaction solution 105 exiting the reactor system 103 after adjustment of the feed water in the aqueous feed stream 101 . The concentration of unreacted N-(phosphonomethyl)iminodiacetic acid in the oxidation reaction solution 105 was 900 ppm by weight. The selectivity of the oxidation reactor system 103 is assumed to be 0.721 pounds of N-(phosphonomethyl)glycine formed for every pound of N-(phosphonomethyl)iminodiacetic acid reacted. Additionally, the oxidation reactor system 103 is assumed to produce 0.00325 pounds of impurity for every pound of N-(phosphonomethyl)glycine formed in the oxidation reactor system. These impurities are assumed to be non-volatile during the process and remain as liquids or become entrapped in crystalline solids or co-crystallize.

The concentration of N-(phosphonomethyl)glycine in the adiabatic crystallizer primary mother liquor decant 112 and in the centrate 123 was 3.5% by weight. The solids concentration in the primary adiabatic crystallization product slurry 113 is assumed to be 25% by weight. The ratio of the adiabatic crystallizer overhead 115 to the primary fraction 107 of the oxidation reaction solution was assumed to be 0.07. The solids content of the wet cake product 119 was 92% by weight.

All liquid/solid separation equipment used in the process is assumed to produce a solids-free liquid, and the decantate from the adiabatic crystallizer 111 is also solids-free.

The partition coefficient of N-(phosphonomethyl)iminodiacetic acid solid in the adiabatic crystallizer 111 is 0.90. The partition coefficient of N-(phosphonomethyl)iminodiacetic acid in the evaporative crystallizer 125 was 0.20. These N-(phosphonomethyl)iminodiacetic acid partition coefficients are defined as the ratio of the concentration of N-(phosphonomethyl)iminodiacetic acid in the solid to that of the N-(phosphonomethyl)iminodiacetic acid in the liquid phase. The ratio of the concentration of diacetic acid, where the concentration in the solid phase is calculated on the basis of N-(phosphonomethyl)glycine only. The impurity partition coefficient in the evaporative crystallizer 125 is 0.60 relative to the non-volatile impurities produced in the oxidation reactor system. This partition coefficient is defined as the ratio of the concentration of the impurity in the solid to the concentration of the impurity in the liquid phase, where the concentration of the impurity in the solid phase is calculated on the basis of N-(phosphonomethyl)glycine only. The partition coefficient of non-volatile impurities in the adiabatic crystallizer 111 is assumed to be negligible.

The solids content of the secondary evaporation crystallization slurry 126 was 15% by weight. Centrates 147A, 147B, and 134 contained 7% by weight N-(phosphonomethyl)glycine.

The assumed ratio of the solids concentration in the concentrated slurry 137 to the solids concentration in the second fraction 131 of the secondary evaporation crystallization slurry is 1.7.

The solids content of the first fraction wet cake product 153 was 70% by weight and the solids content of the second wet cake product 151 was 88% by weight.

These calculations again assume that 2500 ppm (by weight) of volatile reaction by-products are present in the oxidation reactor solution 105 in the model simulations. These volatile components may remain in the overhead streams from adiabatic crystallizer 111 and evaporative crystallizer 125 . The concentration of volatile impurities in the respective crystallizer overhead effluents is assumed to be equal to the concentration of volatile impurities in the total feed to adiabatic crystallizer 111 and evaporative crystallizer 125 .

Example A: This is a simulated mass balance for a process configuration similar to that shown in Figure 2, where the second wet cake product 151 accounted for 31.11% by weight of the total N-(phosphonomethyl)glycine production. In this example, the N-(phosphonomethyl)glycine analysis of the second wet cake product 151 was 95.00% by weight (on a dry basis) and the required diabatic evaporative crystallizer overhead 127 was 2.73 lbs/ per pound of N-(phosphonomethyl)iminodiacetic acid added to reactor system 103.

Example B: This is a variation of Example A, but in which the production of the second wet cake 151 is increased to 35.57% by weight of the total N-(phosphonomethyl)glycine production, while the total required non-adiabatic evaporative crystallizer top flow 127 per pound of N-(phosphonomethyl)iminodiacetic acid added to reactor system 103 remained about the same. In this example, the N-(phosphonomethyl)glycine analysis of the second wet cake product 151 dropped to 93.91% by weight (on a dry basis). Example B illustrates a limitation in the production rate of a second wet cake product 151 of acceptable purity.

Example C: This is another variation on the basis of examples A and B, except that the output of the second wet cake 151 is further improved to 41.90% of the total output of N-(phosphonomethyl) glycine, and with more production tasks delivered To the non-adiabatic crystallizer 125, the amount of make-up water in the aqueous feed stream 101 is increased. In this example, the N-(phosphonomethyl)glycine analytical value of the second wet cake product 151 is similar to the corresponding value in Example A, but this is at the desired increase in the diabatic evaporative crystallizer overhead 127 This was achieved at a cost of 3.69 lbs/lb of N-(phosphonomethyl)iminodiacetic acid added to reactor system 103. Example C illustrates that a higher production rate of the second wet cake product 151 can be achieved by delegating more production to the non-adiabatic crystallizer, but at the expense of increasing the demand on the top effluent 127 of the non-adiabatic evaporative crystallizer (i.e. , at the expense of increasing the operating cost of the non-adiabatic evaporative crystallizer).

Examples A to C illustrate that increasing the percentage of the second wet cake product 151 in FIG. This is achieved at the expense of the additional requirement for the diadiabatic evaporative crystallizer overhead 127 (Example C).

Example D: This is a simulated mass balance for a process configuration similar to that shown in FIG. The evaporative crystallization slurry 126 in the evaporative crystallizer centrifuge feed tank 141 is mixed. In this example, 42% of the yield could be produced as the second wet cake product 151, which had a higher N-(phosphonomethyl)glycine assay value than in Example A (which produced a lower The analytical values in the second wet cake percent), and the requirements for the diadiabatic evaporative crystallizer overhead 127 will be slightly reduced compared to Example A. This illustrates how mixing the primary crystallization product slurry 113 from the adiabatic crystallizer with the evaporative crystallization slurry 126 from the non-adiabatic evaporative crystallizer can result in increased production of the second wet cake 151 without increasing the requirement for the non-adiabatic evaporative crystallizer. Evaporative crystallizer overhead 127 requires and/or does not require sacrificing wet cake purity.

Example E: This example is similar to Example D, except that according to Figure 5, the wet cake product 119 recovered from the basket centrifuge 117, rather than the primary crystallization product slurry 113 from the adiabatic crystallizer, is diverted and compared with The evaporative crystallization slurry 126 from the adiabatic evaporative crystallizer 125 is mixed in the evaporative crystallizer centrifuge feed tank 141 . In this example, a similar purity and yield of the second wet cake product 151 as in Example D was obtained, but with reduced requirements on the diabatic evaporative crystallizer overhead 127.

Table 2 below summarizes the input and model calculated values for simulating mass balances in Examples A through E.

Table 2 example Water (lb/100 lbGI) in aqueous feed stream 101 added to reactor system 103 ^** Weight % Gly in oxidation reaction solution 105 ^* Ratio of primary fraction 107 to reaction solution 105 ^* % of primary product slurry 113 sent to feed tank 141 ^* Non-adiabatic crystallizer overhead 127 (lb/lb GI) ^** % of total production as wet cake 151 ^** % from wet cake 151 in adiabatic crystallizer ^** Wet Cake 151Gly Analysis (wt%, dry basis) ^** Wet Cake 121Gly Analysis (wt%, dry basis) ^** % of non-adiabatic crystallizer slurry 126 fed to non-porous drum centrifuge 133 ^* Ratio of centrate 134 sent to wet cake 121 to 134 recycled to non-adiabatic crystallizer 125 ^* A 337.00 9.1% 0.69 0.0% 2.73 31.11% 0.00% 95.00% 97.30% 20% 0.7 B 337.00 9.1% 0.69 0.0% 2.79 35.57% 0.00% 93.91% 98.04% 10% 0.75 C 418.00 9.1% 0.57 0.0% 3.69 41.90% 0.00% 94.99% 97.90% 20% 0.18 D. 314.42 9.1% 0.76 25.0% 2.48 42.55% 28.22% 95.94% 97.17% 20% 0.5 E. 293.55 9.1% 0.75 25.0% 2.28 42.53% 28.25% 95.99% 97.15% 20% 0.5

^* user input

^** model calculation

The present invention is not limited to the above embodiments, and various modifications can be made respectively. The purpose of the above description of the preferred embodiment is merely to give those skilled in the art an understanding of the invention, its principles and their practical application, so that those skilled in the art may adapt and employ the invention in many forms for use in requirements for specific uses.

With regard to the use of the words "comprises" or "comprises" throughout this specification (including the appended claims), it should be noted that unless otherwise required herein, these words are used on a basic and clear understanding that they include and Not to be construed exclusively, and it is intended that each of these words be so construed when read throughout the specification.

Claims (69)

1. method that from the oxidizing reaction aqueous solution that comprises N-((phosphonomethyl)) glycine product, reclaims N-((phosphonomethyl)) glycine product, this method comprises:

Reacting solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

N-((phosphonomethyl)) glycine product crystal precipitates the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor to produce from elementary fraction;

Elementary product slurry is divided into first part and second section;

Therefore the N-of precipitation separation ((phosphonomethyl)) glycine product crystal from the first part of described elementary product slurry produces the wet cake product of a N-((phosphonomethyl)) glycine;

With the second section of elementary product slurry and N-((phosphonomethyl)) glycine product blending contained in the secondary fraction of described reacting solution;

Allow the secondary fraction of described reacting solution carry out the evaporative crystallization operation, therefore produce the dual evaporation product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and secondary mother liquor from the secondary fraction, to be settled out N-((phosphonomethyl)) glycine product crystal; With

From described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of the 2nd N-((phosphonomethyl)) glycine.

2. method according to claim 1, wherein elementary fraction by under adiabatic condition basically therefrom vaporize water cool off from elementary fraction, to be settled out N-((phosphonomethyl)) glycine product crystal and to produce the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor.

3. method according to claim 1; the secondary fraction blending of the second section of wherein said elementary product slurry and described reacting solution is carried out described evaporative crystallization operation to be settled out N-((phosphonomethyl)) glycine product crystal and therefore to produce described dual evaporation product slurry from the evaporative crystallizer raw mix to form evaporative crystallizer raw mix and described evaporative crystallizer raw mix.

4. method according to claim 3, wherein this method further comprises:

Dual evaporation product slurry is divided into a plurality of fractions that comprise first fraction and second fraction;

From first fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce first fraction of the wet cake product of N-((phosphonomethyl)) glycine; With

From second fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal to produce described the 2nd N-(phosphonomethyl)) the wet cake product of glycine, the wet cake product of the 2nd N-((phosphonomethyl)) glycine has than the wet higher solids content of cake product of first fraction.

5. according to the method for claim 4; wherein sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from second fraction of described dual evaporation product slurry in centrifugal basket drier and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from first fraction of described dual evaporation product slurry in solid bowl formula whizzer.

6. method according to claim 4; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.1.

7. method according to claim 6; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.2.

8. method according to claim 7; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.25.

9. method according to claim 4, wherein wet cake product of first fraction N-((phosphonomethyl)) glycine and the wet cake product blending of a N-((phosphonomethyl)) glycine.

10. according to the method for claim 4, wherein in the first wet cake product or N-((phosphonomethyl)) glycine in the wet cake product of first fraction with one or more alkali neutralizations with the agricultural for preparing N-((phosphonomethyl)) glycine on acceptable salt.

11. method according to claim 1; at least a portion blending of the second section of wherein said elementary product slurry and described dual evaporation product slurry is with formation secondary fraction product mixtures, and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from described secondary fraction product mixtures to produce the wet cake product of described the 2nd N-((phosphonomethyl)) glycine.

12. according to the method described in the claim 11, wherein this method further comprises:

Dual evaporation product slurry is divided into a plurality of fractions that comprise first fraction and second fraction;

From first fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of first fraction N-((phosphonomethyl)) glycine; With

To form described secondary fraction product mixtures, the wet cake product of the 2nd N-((phosphonomethyl)) glycine has than the wet higher solids content of cake product of first fraction with the second fraction blending of the second section of described elementary product slurry and described dual evaporation product slurry.

13. method according to claim 12; wherein sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from described secondary fraction product mixtures in centrifugal basket drier and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from first fraction of described dual evaporation product slurry in solid bowl formula whizzer.

14. method according to claim 12; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.1.

15. method according to claim 14; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.2.

16. method according to claim 15; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.25.

17. method according to claim 12, wherein wet cake product of first fraction N-((phosphonomethyl)) glycine and the wet cake product blending of a N-((phosphonomethyl)) glycine.

18. according to the method for claim 12, acceptable salt on wherein N-((phosphonomethyl)) glycine in the first wet cake product or in first fraction wets the cake product neutralizes with the agricultural of preparation N-((phosphonomethyl)) glycine with one or more alkali.

19. a method that reclaims N-((phosphonomethyl)) glycine product from the oxidizing reaction aqueous solution that comprises N-((phosphonomethyl)) glycine product, this method comprises:

Reacting solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

N-((phosphonomethyl)) glycine product crystal is precipitated the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor to produce from elementary fraction;

From described elementary product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of a N-((phosphonomethyl)) glycine;

At least a portion and N-((phosphonomethyl)) glycine product blending contained in the secondary fraction of described reacting solution with the wet cake product of a described N-((phosphonomethyl)) glycine;

Allow the secondary fraction of described reacting solution carry out the evaporative crystallization operation, therefore produce the dual evaporation product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and secondary mother liquor from described secondary fraction, to precipitate N-((phosphonomethyl)) glycine product crystal;

From described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of the 2nd N-((phosphonomethyl)) glycine.

20. method according to claim 19, wherein elementary fraction be by under adiabatic condition basically therefrom vaporize water cool off from elementary fraction, to be settled out N-((phosphonomethyl)) glycine product crystal and to produce the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor.

21. method according to claim 19; at least a portion of the wet cake product of a wherein said N-((phosphonomethyl)) glycine and at least a portion blending of described dual evaporation product slurry to be forming secondary fraction product mixtures, and sedimentary N-((phosphonomethyl)) glycine product crystal is separated from described secondary fraction product mixtures to produce described the 2nd N-((phosphonomethyl)) the glycine cake product that wets.

22. according to the method described in the claim 21, wherein this method further comprises:

Dual evaporation product slurry is divided into a plurality of fractions that comprise first fraction and second fraction;

From first fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of first fraction N-((phosphonomethyl)) glycine; With

Forming secondary fraction product mixtures, the wet cake product of the 2nd N-((phosphonomethyl)) glycine has than the first fraction higher solids content of cake product that wets with the second fraction blending of at least a portion of the wet cake product of a described N-((phosphonomethyl)) glycine and described dual evaporation product slurry.

23. method according to claim 22; wherein sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from described secondary fraction product mixtures in centrifugal basket drier and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from first fraction of described dual evaporation product slurry in solid bowl formula whizzer.

24. method according to claim 22; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.1.

25. method according to claim 24; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.2.

26. method according to claim 25; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.25.

27. method according to claim 22, wherein wet cake product of first fraction N-((phosphonomethyl)) glycine and the wet cake product blending of a N-((phosphonomethyl)) glycine.

28. according to the method for claim 22, acceptable salt on wherein N-((phosphonomethyl)) glycine in the first wet cake product or in first fraction wets the cake product neutralizes with the agricultural of preparation N-((phosphonomethyl)) glycine with one or more alkali.

29. method according to claim 19; the at least a portion of the wet cake product of a wherein said N-((phosphonomethyl)) glycine and the secondary fraction blending of described reacting solution are carried out described evaporative crystallization operation to be settled out N-((phosphonomethyl)) glycine product crystal and therefore to produce described dual evaporation product slurry from the evaporative crystallizer raw mix to form evaporative crystallizer raw mix and this evaporative crystallizer raw mix.

30. method according to claim 29, wherein this method further comprises:

Dual evaporation product slurry is divided into a plurality of fractions that comprise first fraction and second fraction;

From first fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of first fraction N-((phosphonomethyl)) glycine; With

From second fraction of described dual evaporation product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal to produce described the 2nd N-(phosphonomethyl)) the wet cake product of glycine, the wet cake product of the 2nd N-((phosphonomethyl)) glycine has than the wet higher solids content of cake product of first fraction.

31. method according to claim 30; wherein sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from second fraction of described dual evaporation product slurry in centrifugal basket drier and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from first fraction of described dual evaporation product slurry in solid bowl formula whizzer.

32. method according to claim 30; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.1.

33. method according to claim 32; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.2.

34. method according to claim 33; wherein measured according to solid weight percentage in described wet cake product, the ratio of the solids content of the solids content of the wet cake product of the 2nd N-((phosphonomethyl)) glycine and the wet cake product of first fraction N-((phosphonomethyl)) glycine is at least about 1.25.

35. method according to claim 30, wherein wet cake product of first fraction N-((phosphonomethyl)) glycine and the wet cake product blending of a N-((phosphonomethyl)) glycine.

36. according to the method for claim 30, acceptable salt on wherein N-((phosphonomethyl)) glycine in the first wet cake product or in first fraction wets the cake product neutralizes with the agricultural of preparation N-((phosphonomethyl)) glycine with one or more alkali.

37. a method that reclaims N-((phosphonomethyl)) glycine product from the oxidizing reaction aqueous solution that comprises N-((phosphonomethyl)) glycine product, this method comprises:

Reacting solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

N-((phosphonomethyl)) glycine product crystal is precipitated the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor to produce from elementary fraction;

N-((phosphonomethyl)) glycine product crystal is precipitated from the secondary crystallization raw mix of at least a portion of the secondary fraction that comprises described reacting solution and described elementary product slurry, to produce the secondary products slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and secondary mother liquor; With

From described secondary products slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of N-((phosphonomethyl)) glycine.

38. a method that reclaims N-((phosphonomethyl)) glycine product from the oxidizing reaction aqueous solution that comprises N-((phosphonomethyl)) glycine product, this method comprises:

Reacting solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

N-((phosphonomethyl)) glycine product crystal is precipitated the elementary product slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor to produce from elementary fraction;

N-((phosphonomethyl)) glycine product crystal is precipitated from the water-based secondary crystallization raw mix of the secondary fraction that comprises described reacting solution, to produce the secondary products slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and secondary mother liquor;

With at least a portion blending of at least a portion of described elementary product slurry and described secondary products slurry to produce secondary fraction product mixtures; With

From described secondary fraction product mixtures, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the wet cake product of N-((phosphonomethyl)) glycine.

39. a method that reclaims N-((phosphonomethyl)) glycine product from the oxidizing reaction aqueous solution that comprises N-((phosphonomethyl)) glycine product, this method comprises:

Reacting solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

In first crystallization operation, from elementary fraction, precipitate N-((phosphonomethyl)) glycine product crystal, comprise the elementary product slurry of sedimentary N-((phosphonomethyl)) glycine product crystal and elementary mother liquor with production;

In second crystallization operation, from the secondary fraction, precipitate N-((phosphonomethyl)) glycine product crystal comprises sedimentary N-((phosphonomethyl)) glycine product crystal and secondary mother liquor with production secondary products slurry;

In the first liquid/solid separating step, from described elementary product slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce first wet cake product and the elementary mother liquor fraction;

In the second liquid/solid separating step, from described secondary products slurry, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce second wet cake product and the secondary mother liquor fraction;

With at least a portion recirculation of each mother liquor fraction, so that wherein contained not recovery N-((phosphonomethyl)) glycine product and impurity are incorporated in the described crystallization operation one or two again; With

Keep the foreign matter content of each wet cake product to be lower than the value that is limited, the maintenance of described foreign matter content comprises impurity net transfer contained in a kind of fraction in the middle of the described first and second mother liquor fractions among following: (i) another operation in described first and second crystallization operations; Another step in the (ii) described first and second liquid/solid separating steps; Another kind in the (iii) described first and second wet cake products; Or any combination (i), (ii) and/or (iii).

40. one kind from comprising easily from solution the method for the independent wet cake product of preparation in a kind of solution of crystalline product and undesirable impurity, this method comprises:

Described solution is divided into a plurality of fractions that comprise elementary fraction and secondary fraction;

In first crystallization operation from elementary fraction the precipitated product crystal, comprise the elementary product slurry of sedimentary product crystal and elementary mother liquor with production;

In second crystallization operation from the secondary fraction precipitated product crystal, comprise the secondary products slurry of sedimentary product crystal and secondary mother liquor with production;

In the first liquid/solid separating step, from described elementary product slurry, isolate sedimentary product crystal, therefore produce first wet cake product and the elementary mother liquor fraction;

In the second liquid/solid separating step, from described secondary products slurry, isolate sedimentary product crystal, therefore produce second wet cake product and the secondary mother liquor fraction;

With at least a portion recirculation of each mother liquor fraction, so that wherein contained product and the impurity of not reclaiming is incorporated in the described crystallization operation one or two again; With

Keep the foreign matter content of each wet cake product to be lower than the value that is limited, the maintenance of described foreign matter content comprises: in (i) will be in a kind of fraction in the middle of the described first and second mother liquor fractions contained impurity net transfer another operation in the middle of described first and second crystallization operations; In (ii) will be in a kind of fraction in the middle of the described first and second mother liquor fractions contained impurity net transfer another step in the middle of the described first and second liquid/solid separating steps; (iii) will from a step the described first and second liquid/solid separating steps, obtain than in the wet cake product net transfer of low impurity content another operation in described first and second crystallization operations; (iv) will from a step the described first and second liquid/solid separating steps, obtain than in the wet cake product net transfer of low impurity content another step in the described first and second liquid/solid separating steps; (obtain in v) will an operation from described first and second crystallization operations than in the slurry net transfer of low impurity content another operation in described first and second crystallization operations; (obtain in vi) will an operation from described first and second crystallization operations than in the slurry net transfer of low impurity content another step in the described first and second liquid/solid separating steps; Or (i), (ii), (iii), (iv), (v) and/or (combination vi).

41. a method that reclaims N-((phosphonomethyl)) glycine product from the slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and mother liquor, this method comprises:

Slurry is divided into a plurality of fractions that comprise first sludge fraction and second sludge fraction;

From described first fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the first wet cake product; With

From described second fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the second wet cake product; Measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.1.

42. according to the described method of claim 41, wherein measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.2.

43. according to the described method of claim 42, wherein measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.25.

44., wherein in independent liquid/solid separating device, sedimentary N-((phosphonomethyl)) glycine crystal is separated from described first and second sludge fraction according to the method for claim 41.

45., wherein in independent whizzer, from described first and second sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine crystal abreast according to the method for claim 44.

46. method according to claim 45; wherein sedimentary N-((phosphonomethyl)) glycine crystal is to separate from described first sludge fraction in solid bowl formula whizzer and sedimentary N-((phosphonomethyl)) glycine crystal is to separate from described second sludge fraction in centrifugal basket drier.

47., wherein in a plurality of centrifugal basket driers, from described second sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine crystal according to the method for claim 46.

48. according to the method for claim 41, wherein the second wet cake product has at least about 85 weight % solid solids contents.

49. according to the method for claim 48, wherein the second wet cake product has from about 90 weight % solids to about 99 weight % solid solids contents.

50. according to the method for claim 49, wherein the second wet cake product has from about 95 weight % solids to about 99 weight % solid solids contents.

51. according to the method for claim 41, wherein the first wet cake product has and is lower than about 85 weight % solid solids contents.

52. according to the method for claim 51, wherein the first wet cake product has and is lower than about 75 weight % solid solids contents.

53. according to the method for claim 41, wherein the first wet cake product has from about 70 weight % solids to about 85 weight % solid solids contents.

54. according to the method for claim 41, wherein described first fraction of telling from described slurry accounts for about 20-100% of described slurry.

55. according to the method for claim 54, wherein described first fraction of telling from described slurry accounts for about 40-60% of described slurry.

56. according to the method for claim 55, wherein described first fraction of telling from described slurry accounts for about 50% of described slurry.

57. a method that reclaims N-((phosphonomethyl)) glycine product from the slurry that comprises sedimentary N-((phosphonomethyl)) glycine product crystal and mother liquor, this method comprises:

Described slurry is divided into a plurality of fractions that comprise first sludge fraction and second sludge fraction;

Described first sludge fraction is incorporated in the first liquid/solid separating device;

From described first sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal, therefore produce the first wet cake product;

Described second sludge fraction is incorporated in the second liquid/solid separating device parallel with the described first liquid/solid separating device; With

From described second sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal; therefore produce the second wet cake product; the second wet cake product has than the first wet higher solids content of cake product, measures according to solid weight percentage in described wet cake product.

58. according to the described method of claim 57, wherein measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.1.

59. according to the described method of claim 58, wherein measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.2.

60. according to the described method of claim 59, wherein measured according to solid weight percentage in the described first and second wet cake products, the ratio of the solids content of the solids content of the second wet cake product and the first wet cake product is at least about 1.25.

61., wherein in independent whizzer, from described first and second sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal abreast according to the method for claim 57.

62. method according to claim 61; wherein sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from described first sludge fraction in solid bowl formula whizzer and sedimentary N-((phosphonomethyl)) glycine product crystal is to separate from described second sludge fraction in centrifugal basket drier.

63., wherein in a plurality of centrifugal basket driers, from described second sludge fraction, isolate sedimentary N-((phosphonomethyl)) glycine product crystal according to the method for claim 62.

64. according to the method for claim 57, wherein the second wet cake product has at least about 85 weight % solid solids contents.

65. according to the method for claim 64, wherein the second wet cake product has from about 90 weight % solids to about 99 weight % solid solids contents.

66. according to the method for claim 65, wherein the second wet cake product has from about 95 weight % solids to about 99 weight % solid solids contents.

67. according to the method for claim 57, wherein the first wet cake product has and is lower than about 85 weight % solid solids contents.

68. according to the method for claim 67, wherein the first wet cake product has and is lower than about 75 weight % solid solids contents.

69. according to the method for claim 57, wherein the first wet cake product has from about 70 weight % solids to about 85 weight % solid solids contents.

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